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Easy-plane ferromagnetism in single-crystal ErB$_{2}$ at low temperatures
Authors:
Christoph Resch,
Georg Benka,
Andreas Bauer,
Christian Pfleiderer
Abstract:
We report a study of single crystals of the hexagonal rare-earth diboride ErB$_{2}$ prepared by means of the self-adjusted flux travelling-solvent floating-zone technique. Measurements of the magnetization, ac susceptibility, specific heat, and electrical resistivity consistently establish ferromagnetic order of the Er$^{3+}$ moments below a second-order phase transition at $T_{c} = 14$~K and a ve…
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We report a study of single crystals of the hexagonal rare-earth diboride ErB$_{2}$ prepared by means of the self-adjusted flux travelling-solvent floating-zone technique. Measurements of the magnetization, ac susceptibility, specific heat, and electrical resistivity consistently establish ferromagnetic order of the Er$^{3+}$ moments below a second-order phase transition at $T_{c} = 14$~K and a very strong easy-plane anisotropy. Curie--Weiss fits of the ac susceptibility are characteristic of ferromagnetic coupling within the easy hexagonal basal plane, and antiferromagnetic coupling along $\langle001\rangle$. Under magnetic field within the basal plane the magnetization is reminiscent of a soft ferromagnet that is polarized in fields above a few tenth of a Tesla, vanishing hysteresis and negligible in-plane anisotropy. Under field along $\langle001\rangle$, typical hard-axis behavior is observed with the magnetization increasing only weakly up to a spin-flip transition at $μ_{0}H_{c} = 12$~T. The easy-plane anisotropy emerges below a crossover temperature $T_{x} \approx 50$~K , i.e. a broad paramagnetic temperature range above $T_{c}$ is governed by strongly anisotropic magnetic fluctuations.
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Submitted 28 April, 2025;
originally announced April 2025.
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Magnetocaloric properties of $R_3$Ga$_5$O$_{12}$ ($R$ = Tb,Gd,Nd,Dy)
Authors:
M. Kleinhans,
K. Eibensteiner,
J. C. Leiner,
C. Resch,
L. Worch,
M. A. Wilde,
J. Spallek,
A. Regnat,
C. Pfleiderer
Abstract:
We report the characteristic magnetic properties of several members of the rare-earth garnet family, Gd$_3$Ga$_5$O$_{12}$ (GGG), Dy$_3$Ga$_5$O$_{12}$ (DGG), Tb$_3$Ga$_5$O$_{12}$ (TGG), and Nd$_3$Ga$_5$O$_{12}$ (NGG), and compare their relative potential utility for magnetocaloric cooling, including their minimal adiabatic demagnetization refrigeration (ADR) temperatures and relative cooling parame…
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We report the characteristic magnetic properties of several members of the rare-earth garnet family, Gd$_3$Ga$_5$O$_{12}$ (GGG), Dy$_3$Ga$_5$O$_{12}$ (DGG), Tb$_3$Ga$_5$O$_{12}$ (TGG), and Nd$_3$Ga$_5$O$_{12}$ (NGG), and compare their relative potential utility for magnetocaloric cooling, including their minimal adiabatic demagnetization refrigeration (ADR) temperatures and relative cooling parameters. A main objective of this work concerns the identification of potential improvements over the magnetocaloric properties of GGG for use in low temperature ADR cryostats. Using Tb$^{+3}$ and Dy$^{+3}$ in the rare-earth site offers, in principle, a higher saturation magnetization and Nd$^{+3}$ gives a lower de Gennes factor and therefore potentially reduced magnetic transition temperatures, limiting the useful temperature range. Our results show that Dy$_3$Ga$_5$O$_{12}$ yields an optimal relative cooling parameter ($RCP$) at low applied fields and low limiting temperatures, which would allow for the design of more efficient ADR cryostats.
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Submitted 10 February, 2023; v1 submitted 4 April, 2022;
originally announced April 2022.
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Compositional Studies of Metals with Complex Order by means of the Optical Floating-Zone Technique
Authors:
Andreas Bauer,
Georg Benka,
Andreas Neubauer,
Alexander Regnat,
Alexander Engelhardt,
Christoph Resch,
Sabine Wurmehl,
Christian G. F. Blum,
Tim Adams,
Alfonso Chacon,
Rainer Jungwirth,
Robert Georgii,
Anatoliy Senyshyn,
Björn Pedersen,
Martin Meven,
Christian Pfleiderer
Abstract:
The availability of large high-quality single crystals is an important prerequisite for many studies in solid-state research. The optical floating-zone technique is an elegant method to grow such crystals, offering potential to prepare samples that may be hardly accessible with other techniques. As elaborated in this report, examples include single crystals with intentional compositional gradients…
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The availability of large high-quality single crystals is an important prerequisite for many studies in solid-state research. The optical floating-zone technique is an elegant method to grow such crystals, offering potential to prepare samples that may be hardly accessible with other techniques. As elaborated in this report, examples include single crystals with intentional compositional gradients, deliberate off-stoichiometry, or complex metallurgy. For the cubic chiral magnets Mn$_{1-x}$Fe$_{x}$Si and Fe$_{1-x}$Co$_{x}$Si, we prepared single crystals in which the composition was varied during growth from $x = 0 - 0.15$ and from $x = 0.1 - 0.3$, respectively. Such samples allowed us to efficiently study the evolution of the magnetic properties as a function of composition, as demonstrated by means of neutron scattering. For the archetypical chiral magnet MnSi and the itinerant antiferromagnet CrB$_{2}$, we grew single crystals with varying initial manganese (0.99 to 1.04) and boron (1.95 to 2.1) content. Measurements of the low-temperature properties addressed the correlation between magnetic transition temperature and sample quality. Furthermore, we prepared single crystals of the diborides ErB$_{2}$, MnB$_{2}$, and VB$_{2}$. In addition to high vapor pressures, these materials suffer from peritectic formation, potential decomposition, and high melting temperature, respectively.
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Submitted 18 November, 2021;
originally announced November 2021.