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Floating zone growth of high-purity MgO substrate single crystals
Authors:
Christo Guguschev,
Michael Schulze,
Andrea Dittmar,
Detlef Klimm,
Kaspars Dadzis,
Thomas Schroeder,
Knut Peters,
Aakash Pushp
Abstract:
MgO single crystals with diameters between 3.5 and 5 mm and lengths up to 40 mm were grown by the optical floating zone technique (OFZ). Despite challenging material properties such as the high melting point of 2825 °C, very high evaporation rate and perfect {100} cleaving characteristics, crack-free crystals were grown at high growth rates exceeding 40 mm/h and at high thermal gradients. Chemical…
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MgO single crystals with diameters between 3.5 and 5 mm and lengths up to 40 mm were grown by the optical floating zone technique (OFZ). Despite challenging material properties such as the high melting point of 2825 °C, very high evaporation rate and perfect {100} cleaving characteristics, crack-free crystals were grown at high growth rates exceeding 40 mm/h and at high thermal gradients. Chemical investigations revealed that the OFZ technique is suitable for the preparation of substrate crystals with a purity of 5N to facilitate the development of novel demonstrator devices based on epitaxially grown thin films. The achieved purity level is improved by more than one order of magnitude if compared to commercial MgO substrate single crystals graded as high purity.
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Submitted 23 October, 2025;
originally announced October 2025.
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Observation via spin Seebeck effect of macroscopic magnetic transport from emergent magnetic monopoles
Authors:
Nan Tang,
Stephan Glamsch,
Aisha Aqeel,
Ludwig Scheuchenpflug,
Michael Schulze,
Christoph Liebald,
Daniel Rytz,
Christo Guguschev,
Manfred Albrecht,
Philipp Gegenwart
Abstract:
Magnetic monopoles, elusive in high-energy physics, have been realised as emergent quasiparticles in solid-state systems, where their unique properties hold promise for novel spintronic applications. Magnetic monopoles have been invoked in diverse platforms, including skyrmion lattices, chiral magnets, soft ferromagnets, aritifical nanomagnets. Yet, a demonstration of their role in magnetic transp…
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Magnetic monopoles, elusive in high-energy physics, have been realised as emergent quasiparticles in solid-state systems, where their unique properties hold promise for novel spintronic applications. Magnetic monopoles have been invoked in diverse platforms, including skyrmion lattices, chiral magnets, soft ferromagnets, aritifical nanomagnets. Yet, a demonstration of their role in magnetic transport has remained elusive. Here, we report such an observation via the spin Seebeck effect in the bulk insulating pyrochlore oxide, spin ice $\mathrm{Dy_2Ti_2O_7}$. By applying a thermal gradient perpendicular to a $[111]$-oriented magnetic field, we detect a transverse spin Seebeck voltage marked by a dominant peak at the onset of monopole proliferation, accompanied by a secondary feature and frequency-dependent behavior. Our findings establish a direct link between monopole dynamics and magnetic transport in an insulating medium, establishing a new pathway for probing fractionalized excitations and advancing towards novel spintronic applications.
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Submitted 22 September, 2025;
originally announced September 2025.
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YSGAG: The Ideal Substrate for YIG in Quantum Magnonics
Authors:
Rostyslav O. Serha,
Carsten Dubs,
Christo Guguschev,
Bernd Aichner,
David Schmoll,
Julien Schäfer,
Jaganandha Panda,
Matthias Weiler,
Philipp Pirro,
Michal Urbánek,
Andrii V. Chumak
Abstract:
Quantum magnonics leverages the quantum properties of magnons to advance nanoscale quantum information technologies. Ferrimagnetic yttrium iron garnet (YIG), known for exceptionally long magnon lifetimes, is a cornerstone material typically grown as thin films on gadolinium gallium garnet (GGG) for lattice matching. However, paramagnetic GGG introduces detrimental damping at low temperatures due t…
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Quantum magnonics leverages the quantum properties of magnons to advance nanoscale quantum information technologies. Ferrimagnetic yttrium iron garnet (YIG), known for exceptionally long magnon lifetimes, is a cornerstone material typically grown as thin films on gadolinium gallium garnet (GGG) for lattice matching. However, paramagnetic GGG introduces detrimental damping at low temperatures due to substrate magnetization, undermining quantum applications. Here, we study magnetic damping in a 150$\,$nm-thick YIG film on a yttrium scandium gallium aluminum garnet (YSGAG) substrate, a newly developed diamagnetic alternative to GGG. Using ferromagnetic resonance spectroscopy down to 30$\,$mK, we compare YIG/YSGAG with a conventional YIG/GGG reference system. We demonstrate that the YIG/YSGAG system maintains low damping from 300$\,$K to 30$\,$mK, with $α= 4.29\times10^{-5}$ at room temperature, comparable to the best YIG/GGG films and bulk YIG, with no low-temperature upturn. The diamagnetic substrate eliminates the dissipation mechanisms that dominate on magnetized GGG, preserving low magnetic damping across the full temperature range. Consequently, YSGAG serves as an ideal substrate for YIG films in quantum magnonics and is paving the way for the development of spin-wave-based quantum technologies.
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Submitted 10 November, 2025; v1 submitted 26 August, 2025;
originally announced August 2025.
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Novel diamagnetic garnet-type substrate single crystals for ultralow-damping yttrium iron garnet Y3Fe5O12 films at cryogenic temperatures
Authors:
C. Guguschev,
C. Dubs,
R. Blukis,
O. Surzhenko,
M. Brützam,
R. Koc,
C. Rhode,
K. Berger,
C. Richter,
C. Berryman,
R. O. Serha,
A. V. Chumak
Abstract:
Y3Sc2Ga3O12-Y3Sc2Al3O12 and Y3Sc2Ga3O12-Y3Al5O12 (YSGAG) solid solution single crystals with diameters up to 30 mm and total lengths up to about 100 mm were grown by the conventional Czochralski technique. Rocking curve measurements on polished sections revealed typical FWHM values of about 22 arcsec, which is indicative of relatively high structural quality for a solid-solution crystal. The grown…
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Y3Sc2Ga3O12-Y3Sc2Al3O12 and Y3Sc2Ga3O12-Y3Al5O12 (YSGAG) solid solution single crystals with diameters up to 30 mm and total lengths up to about 100 mm were grown by the conventional Czochralski technique. Rocking curve measurements on polished sections revealed typical FWHM values of about 22 arcsec, which is indicative of relatively high structural quality for a solid-solution crystal. The grown substrate crystals are nearly lattice-matched with Y3Fe5O12 (YIG) to allow epitaxial growth of high-quality thin films. Single crystalline YIG films with thicknesses between 100 nanometer and 2.9 micrometer were successfully grown on epi-polished YSGAG substrates using liquid phase epitaxy (LPE). Selected magnetic and microwave properties of the epitaxial films, which still exhibit small lattice misfits to the substrates, were then studied at room temperature. In addition, initial low-temperature investigations confirm that the YIG/YSGAG system is superior to the conventional YIG/GGG (Gd3Ga5O12) system at temperatures below 10 K, as the ferromagnetic resonance (FMR) linewidth does not increase with decreasing temperature. Therefore, the novel diamagnetic substrates are better suited for microwave applications at low temperature, as excessive damping losses induced by paramagnetic substrates can be avoided. It therefore seems to be a suitable pathway to achieve scalable microwave components for hybrid-integrated quantum systems based on ultralow-damping YIG films that can operate efficiently at millikelvin temperatures.
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Submitted 25 August, 2025;
originally announced August 2025.
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Improper Ferroelectricity at the Monolayer Limit
Authors:
Yilin Evan Li,
Harikrishnan KP,
Haidong Lu,
Rachel A. Steinhardt,
Megan E. Holtz,
Mario Brützam,
Matthew M. Dykes,
Elke Arenholz,
Sankalpa Hazra,
Adriana LaVopa,
Xiaoxi Huang,
Wenwen Zhao,
Piush Behera,
Maya Ramesh,
Evan Krysko,
Venkatraman Gopalan,
Ramamoorthy Ramesh,
Craig J. Fennie,
Robert J. Cava,
Christo Guguschev,
Alexei Gruverman,
David A. Muller,
Darrell G. Schlom
Abstract:
Ultrathin ferroelectric films with out-of-plane polarization and high Curie temperatures are key to miniaturizing electronic devices. Most ferroelectrics employed in devices are proper ferroelectrics, where spontaneous polarization is the primary order parameter. Unfortunately, the Curie temperature of proper ferroelectrics is drastically reduced as the ferroelectric becomes thin; nearly all prope…
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Ultrathin ferroelectric films with out-of-plane polarization and high Curie temperatures are key to miniaturizing electronic devices. Most ferroelectrics employed in devices are proper ferroelectrics, where spontaneous polarization is the primary order parameter. Unfortunately, the Curie temperature of proper ferroelectrics is drastically reduced as the ferroelectric becomes thin; nearly all proper ferroelectrics need to be thicker than several unit cells. The absence of an ultrathin limit has been predicted, but not verified for improper ferroelectrics. These are ferroelectrics where the polarization emerges secondary to the primary order parameter, such as a structural distortion. Here we report improper ferroelectricity with an undiminished Curie temperature in a 0.75-unit-cell-thick hexagonal LuFeO3 (h-LuFeO3) film grown on a SrCo2Ru4O11 bottom electrode with an atomically engineered monolayer bridging layer. Our results demonstrate the absence of a critical thickness for improper ferroelectricity and provide a methodology for creating ultrathin improper ferroelectrics by stabilizing their primary order parameters.
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Submitted 8 March, 2025;
originally announced March 2025.
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Soft phonon and the central peak at the cubic-to-tetragonal phase transition in SrTiO$_3$
Authors:
Avishek Maity,
Klaus Habicht,
Michael Merz,
Ayman H. Said,
Christo Guguschev,
Danny Kojda,
Britta Ryll,
Jan-Ekkehard Hoffmann,
Andrea Dittmar,
Thomas Keller,
Frank Weber
Abstract:
The continuous displacive phase transition in SrTiO$_3$ near $T_c \approx 105$ K features a central elastic peak in neutron scattering investigations at temperatures above $T_c$, i.e., before the corresponding soft phonon mode is overdamped upon cooling. The origin of this central peak is still not understood. Here, we report an inelastic x-ray scattering investigation of the cubic-to-tetragonal p…
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The continuous displacive phase transition in SrTiO$_3$ near $T_c \approx 105$ K features a central elastic peak in neutron scattering investigations at temperatures above $T_c$, i.e., before the corresponding soft phonon mode is overdamped upon cooling. The origin of this central peak is still not understood. Here, we report an inelastic x-ray scattering investigation of the cubic-to-tetragonal phase transition in SrTiO$_3$. We compare quantitatively measurements of the soft phonon mode on two differently grown samples and discuss the findings regarding results from thermodynamic and transport probes such as specific heat and thermal conductivity. Furthermore, we use inelastic x-ray scattering to perform elastic scans with both high momentum- and milli-electronvolt energy-resolution and, thus, be able to separate elastic intensities of the central peak from low-energy quasielastic phonon scattering. Our results indicate that the evolution of the soft mode is similar in both samples though the intensities of the central peak differ by a factor of four. Measurements revealing anisotropic correlation lengths on cooling towards $T_c$, indicate that local properties of the crystals to which collective lattice excitations are insensitive are likely at the origin of the central elastic line in SrTiO$_3$.
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Submitted 29 March, 2025; v1 submitted 20 February, 2025;
originally announced February 2025.
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Picosecond expansion in LaAlO3 resonantly driven by infrared-active phonons
Authors:
Jakob Gollwitzer,
Jeffrey Z. Kaaret,
Y. Eren Suyolcu,
Guru Khalsa,
Rylan C. Fernandes,
Oleg Gorobtsov,
Sören Buchenau,
ChanJu You,
Jayanti Higgins,
Ryan S. Russell,
Ziming Shao,
Yorick A. Birkhölzer,
Takahiro Sato,
Matthieu Chollet,
Giacomo Coslovich,
Mario Brützam,
Christo Guguschev,
John W. Harter,
Ankit S. Disa,
Darrell G. Schlom,
Nicole A. Benedek,
Andrej Singer
Abstract:
We investigate the ultrafast structural dynamics of LaAlO3 thin films driven by short mid-infrared laser pulses at 20 THz. Time-resolved X-ray diffraction reveals an immediate lattice expansion and an acoustic breathing mode of the film. First-principles theory and a spring-mass model identify the direct coupling between coherently driven infrared-active phonons and strain as the underlying mechan…
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We investigate the ultrafast structural dynamics of LaAlO3 thin films driven by short mid-infrared laser pulses at 20 THz. Time-resolved X-ray diffraction reveals an immediate lattice expansion and an acoustic breathing mode of the film. First-principles theory and a spring-mass model identify the direct coupling between coherently driven infrared-active phonons and strain as the underlying mechanism. Time-resolved optical birefringence measurements confirm that the amplitude of this acoustic mode scales linearly with the pump fluence, which agrees with the theory. Furthermore, time-resolved X-ray diffuse scattering indicates that THz excitation enhances crystallinity by inducing a non-thermal increase in structural symmetry originating from preexisting defects. These findings highlight the potential of a multimodal approach-combining time-resolved X-ray and optical measurements and first-principles theory-to elucidate and control structural dynamics in nanoscale materials.
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Submitted 22 December, 2024;
originally announced December 2024.
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Single crystal growth and characterization of Ba$_2$ScNbO$_6$ -- a novel substrate for BaSnO$_3$ films
Authors:
C. Guguschev,
D. Klimm,
M. Brützam,
T. M. Gesing,
M. Gogolin,
H. Paik,
A. Dittmar,
V. J. Fratello,
D. G. Schlom
Abstract:
Large single crystals of the double-perovskite Ba$_2$ScNbO$_6$ were grown from the melt for the first time. With a lattice parameter at room temperature of 4.11672(1) Å, this cubic double-perovskite has an excellent lattice match to BaSnO$_3$, PbZr$_{0.9}$Ti$_{0.1}$O$_3$, LaInO$_3$, BiScO$_3$, and other perovskites of contemporary interest. Differential thermal analysis showed that Ba$_2$ScNbO…
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Large single crystals of the double-perovskite Ba$_2$ScNbO$_6$ were grown from the melt for the first time. With a lattice parameter at room temperature of 4.11672(1) Å, this cubic double-perovskite has an excellent lattice match to BaSnO$_3$, PbZr$_{0.9}$Ti$_{0.1}$O$_3$, LaInO$_3$, BiScO$_3$, and other perovskites of contemporary interest. Differential thermal analysis showed that Ba$_2$ScNbO$_6$ melts at 2165$\pm$30°C in an inert atmosphere. Competitive grain growth was visualized by energy dispersive Laue mapping. X-ray diffraction rocking curve measurements revealed full width at half maximum values between 21 and 33 arcsec for 002 and 004 reflections. The crystals were sufficiently large to yield (100)-oriented single-crystal substrates with surface areas as large as 10 x 10 mm$^2$.
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Submitted 5 July, 2019;
originally announced July 2019.
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Thermal analysis and crystal growth of doped Nb$_2$O$_5$
Authors:
Julia Hidde,
Christo Guguschev,
Detlef Klimm
Abstract:
The systems Nb$_2$O$_5$-Ta$_2$O$_5$ and Nb$_2$O$_5$-V$_2$O$_5$ were investigated using thermal analysis, X-ray powder diffraction and thermodynamic simulations. Solid solution formation is possible for both systems; furthermore, both contain one intermediate compound, VNb$_9$O$_{25}$ or Ta$_2$Nb$_4$O$_{15}$, respectively. Phase relationships for pure niobium(V)-oxide and tantalum(V)-oxide were stu…
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The systems Nb$_2$O$_5$-Ta$_2$O$_5$ and Nb$_2$O$_5$-V$_2$O$_5$ were investigated using thermal analysis, X-ray powder diffraction and thermodynamic simulations. Solid solution formation is possible for both systems; furthermore, both contain one intermediate compound, VNb$_9$O$_{25}$ or Ta$_2$Nb$_4$O$_{15}$, respectively. Phase relationships for pure niobium(V)-oxide and tantalum(V)-oxide were studied under ambient pressure. It was found that both compounds can occur in two stable solid modifications. For niobium(V)-oxide this are the monoclinic high-temperature modification (H-Nb$_2$O$_5$) and an orthorhombic low-temperature modification (T-Nb$_2$O$_5$) and for tantalum(V)-oxide a tetragonal high-temperature form ($α$-Ta$_2$O$_5$) and an orthorhombic low-temperature form ($β$-Ta$_2$O$_5$). Based on these results, crystal growth experiments with various compositions from both systems were carried out using the optical floating zone (OFZ) technique.
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Submitted 8 October, 2018; v1 submitted 5 October, 2018;
originally announced October 2018.
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Investigation of the Nd$_2$O$_3$--Lu$_2$O$_3$--Sc$_2$O$_3$ phase diagram for the preparation of perovskite-type mixed crystals NdLu$_{1-x}$Sc$_x$O$_3$
Authors:
Tamino Hirsch,
Christo Guguschev,
Albert Kwasniewski,
Steffen Ganschow,
Detlef Klimm
Abstract:
Based on differential thermal analysis (DTA) and X-ray powder diffraction (XRD), a description of the system Nd$_2$O$_3$--Lu$_2$O$_3$--Sc$_2$O$_3$ was obtained by thermodynamic assessment. Four fields of primary crystallization could be identified; from melt compositions close to the Lu$_2$O$_3$--Sc$_2$O$_3$ edge the rare-earth oxide C-phase crystallizes first, which is stable down to room tempera…
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Based on differential thermal analysis (DTA) and X-ray powder diffraction (XRD), a description of the system Nd$_2$O$_3$--Lu$_2$O$_3$--Sc$_2$O$_3$ was obtained by thermodynamic assessment. Four fields of primary crystallization could be identified; from melt compositions close to the Lu$_2$O$_3$--Sc$_2$O$_3$ edge the rare-earth oxide C-phase crystallizes first, which is stable down to room temperature. From Nd$_2$O$_3$ rich melts the X-phase forms, which is stable only at high temperatures. An additional field, where the alternative high-temperature phase H solidifies as primary product touches the Nd$_2$O$_3$--Lu$_2$O$_3$ edge of the concentration triangle. From melts close to the composition NdScO$_3$, the P-phase (perovskite) can be crystallized and mixed crystals with second end member NdLuO$_3$ have been grown from the melt. Crystals of this mixed perovskite were grown by the micro-pulling-down and Czochralski methods.
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Submitted 14 June, 2018;
originally announced June 2018.
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On melt solutions for the growth of CaTiO$_3$ crystals
Authors:
Detlef Klimm,
Max Schmidt,
Nora Wolff,
Christo Guguschev,
Steffen Ganschow
Abstract:
When calcium titanate crystals are grown from stoichiometric melts, they crystallize in the cubic perovskite structure. Upon cooling to room temperature they undergo subsequent phase transitions to tetragonal and orthorhombic modifications. These phase transitions are disruptive and result in severely damaged crystals. This paper presents differential thermal analysis data for several prospective…
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When calcium titanate crystals are grown from stoichiometric melts, they crystallize in the cubic perovskite structure. Upon cooling to room temperature they undergo subsequent phase transitions to tetragonal and orthorhombic modifications. These phase transitions are disruptive and result in severely damaged crystals. This paper presents differential thermal analysis data for several prospective solvents, with the aim to identify a system offering the possibility to perform crystal growth of undistorted CaTiO$_3$ crystals by crystallizing them significantly below the melting point directly in the low temperature modification. From mixtures CaF$_2$:TiO$_2$:CaTiO$_3$ = 3:1:1 (molar ratio) the growth of undistorted, at least millimeter-sized CaTiO$_3$ crystals is possible.
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Submitted 1 February, 2018; v1 submitted 12 January, 2018;
originally announced January 2018.
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Thermal conductivity of rare-earth scandates in comparison to other oxidic substrate crystals
Authors:
Julia Hidde,
Christo Guguschev,
Steffen Ganschow,
Detlef Klimm
Abstract:
High-temperature thermal properties of three neighboring rare-earth scandates DyScO$_3$, TbScO$_3$ and GdScO$_3$ were compared to La$_{0.29}$Sr$_{0.71}$Al$_{0.65}$Ta$_{0.35}$O$_3$ (LSAT) and sapphire. To calculate thermal conductivity, heat capacity and thermal diffusivity were measured by differential scanning calorimetry and laser flash technique, respectively. DyScO$_3$ and TbScO$_3$ showed an…
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High-temperature thermal properties of three neighboring rare-earth scandates DyScO$_3$, TbScO$_3$ and GdScO$_3$ were compared to La$_{0.29}$Sr$_{0.71}$Al$_{0.65}$Ta$_{0.35}$O$_3$ (LSAT) and sapphire. To calculate thermal conductivity, heat capacity and thermal diffusivity were measured by differential scanning calorimetry and laser flash technique, respectively. DyScO$_3$ and TbScO$_3$ showed an untypical rise in the thermal conductivity above 900\,K, while for GdScO$_3$, LSAT and sapphire the expected decrease at elevated temperatures could be observed. These results lead to the proposal of a new type of heat transport by migrating ions.
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Submitted 3 November, 2017;
originally announced November 2017.
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Crystal growth and characterization of the pyrochlore Tb$_2$Ti$_2$O$_7$
Authors:
D. Klimm,
C. Guguschev,
D. J. Kok,
M. Naumann,
L. Ackermann,
D. Rytz,
M. Peltz,
K. Dupré,
M. D. Neumann,
A. Kwasniewski,
D. G. Schlom,
M. Bickermann
Abstract:
Terbium titanate (Tb$_2$Ti$_2$O$_7$) is a spin-ice material with remarkable magneto-optical properties. It has a high Verdet constant and is a promising substrate crystal for the epitaxy of quantum materials with the pyrochlore structure. Large single crystals with adequate quality of Tb$_2$Ti$_2$O$_7$ or any pyrochlore are not available so far. Here we report the growth of high-quality bulk cryst…
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Terbium titanate (Tb$_2$Ti$_2$O$_7$) is a spin-ice material with remarkable magneto-optical properties. It has a high Verdet constant and is a promising substrate crystal for the epitaxy of quantum materials with the pyrochlore structure. Large single crystals with adequate quality of Tb$_2$Ti$_2$O$_7$ or any pyrochlore are not available so far. Here we report the growth of high-quality bulk crystals using the Czochralski method to pull crystals from the melt. Prior work using the automated Czochralski method has suffered from growth instabilities like diameter fluctuation, foot formation and subsequent spiraling shortly after the seeding stage. In this study, the volumes of the crystals were strongly increased to several cubic centimeters by means of manual growth control, leading to crystal diameters up to 40 mm and crystal lengths up to 10 mm. Rocking curve measurements revealed full width at half maximum values between 28 and 40" for 222 reflections. The specific heat capacity c$_p$ was measured between room temperature and 1573 K by dynamic differential scanning calorimetry and shows the typical slow parabolic rise. In contrast, the thermal conductivity κ(T) shows a minimum near 700 K and increases at higher temperature T. Optical spectroscopy was performed at room temperature from the ultraviolet to the near infrared region, and additionally in the near infrared region up to 1623 K. The optical transmission properties and the crystal color are interpreted to be influenced by partial oxidation of Tb$^{3+}$ to Tb$^{4+}$.
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Submitted 20 June, 2017; v1 submitted 18 May, 2017;
originally announced May 2017.
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Single crystal fiber growth of cerium doped strontium yttrate, SrY2O4:Ce3+
Authors:
Jan Philippen,
Christo Guguschev,
Detlef Klimm
Abstract:
First single crystal fibers of cerium doped strontium yttrate are fabricated using the laser-heated pedestal growth technique. Through thermodynamic equilibrium calculations and by high-temperature mass spectrometry suitable growth conditions can be determined. The atmosphere plays an important role during crystallization. It affects the composition shift, on the one hand, and the valence state of…
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First single crystal fibers of cerium doped strontium yttrate are fabricated using the laser-heated pedestal growth technique. Through thermodynamic equilibrium calculations and by high-temperature mass spectrometry suitable growth conditions can be determined. The atmosphere plays an important role during crystallization. It affects the composition shift, on the one hand, and the valence state of cerium, on the other hand. These properties can be explained by combining X-ray diffraction, elemental analysis, and optical spectroscopy. Crystallization in slightly reducing nitrogen atmosphere proves to be a reasonable choice, because evaporation is suppressed and trivalent cerium is stabilized. Strong green emission that depends on the oxygen fugacity during crystallization can be excited using UV light. Optical transmission of SrY2O4:Ce3+ is measured for the first time.
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Submitted 29 January, 2014;
originally announced January 2014.
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Top-seeded solution growth of SrTiO3 crystals and phase diagram studies in the SrO-TiO2 system
Authors:
Christo Guguschev,
Detlef Klimm,
Frank Langhans,
Zbigniew Galazka,
Dirk Kok,
Uta Juda,
Reinhard Uecker
Abstract:
The TiO2 rich part of the (1-x) SrO + x TiO2 phase diagram 0.5 <= x <= 1.0 was redetermined and the eutectic point between SrTiO3 and TiO2 was found at x_eut=0.7700+/-0.0001; T_eut=(1449+/-3) deg C. From TiO2 rich melt solutions, x=0.75 centimeter-sized single crystals could be grown. The best crystals with etch pit density <2 x 10^4/cm^2 were obtained for growth directions <110> and <100>. AFM in…
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The TiO2 rich part of the (1-x) SrO + x TiO2 phase diagram 0.5 <= x <= 1.0 was redetermined and the eutectic point between SrTiO3 and TiO2 was found at x_eut=0.7700+/-0.0001; T_eut=(1449+/-3) deg C. From TiO2 rich melt solutions, x=0.75 centimeter-sized single crystals could be grown. The best crystals with etch pit density <2 x 10^4/cm^2 were obtained for growth directions <110> and <100>. AFM investigation of the interface reveals layer-by-layer growth.
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Submitted 8 November, 2013; v1 submitted 8 October, 2013;
originally announced October 2013.
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Laser-heated pedestal growth of cerium doped calcium scandate crystal fibers
Authors:
J. Philippen,
C. Guguschev,
R. Bertram,
D. Klimm
Abstract:
Ce3+ doped oxide materials are promising for optical emission in the green spectral range. The growth of CaSc2O4:Ce3+ single crystals is reported here for the first time. Laser heated pedestal growth (LHPG) proved to be suitable for this refractive material, if performed in nitrogen of 99.999% purity. If the oxygen content of the growth atmosphere is substantially larger, Ce4+ is formed, which sho…
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Ce3+ doped oxide materials are promising for optical emission in the green spectral range. The growth of CaSc2O4:Ce3+ single crystals is reported here for the first time. Laser heated pedestal growth (LHPG) proved to be suitable for this refractive material, if performed in nitrogen of 99.999% purity. If the oxygen content of the growth atmosphere is substantially larger, Ce4+ is formed, which shows no useful optical emission. If the oxygen content is substantially lower, severe evaporation of calcium impedes stable crystal growth. Thermodynamic equilibrium calculations allowed to describe evaporation of species and cerium dopant charging under different growth conditions. The evaporation could be investigated by quadrupole mass spectrometry of emanating gases and by chemical analysis of fibers with ICP-OES. The congruent melting point was confirmed by DTA at 2110 degrees centigrade. Photoluminescence spectrometry of fibers revealed the dependence of optical emission in the green spectral range on growth conditions.
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Submitted 10 December, 2012;
originally announced December 2012.