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DDC: 620 × Subject: Magnetic materials ×

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    Phase transition and anomalous low temperature ferromagnetic phase in Pr 0.6Sr 0.4MnO 3 single crystals
    (New York, NY : Springer Science + Business Media B.V., 2009) Rößler, S.; Harikrishnan, S.; Naveen Kumar, C.M.; Bhat, H.L.; Elizabeth, S.; Rößler, U.K.; Steglich, F.; Wirth, S.
    We report on the magnetic and electrical properties of Pr 0.6Sr 0.4MnO 3 single crystals. This compound undergoes a continuous paramagnetic-ferromagnetic transition with a Curie temperature T C301 K and a first-order structural transition at T S64 K. At T S, the magnetic susceptibility exhibits an abrupt jump, and a corresponding small hump is seen in the resistivity. The critical behavior of the static magnetization and the temperature dependence of the resistivity are consistent with the behavior expected for a nearly isotropic ferromagnet with short-range exchange belonging to the Heisenberg universality class. The magnetization (M-H) curves below T S are anomalous in that the virgin curve lies outside the subsequent M-H loops. The hysteretic structural transition at T S as well as the irreversible magnetization processes below T S can be explained by phase separation between a high-temperature orthorhombic and a low-temperature monoclinic ferromagnetic phase.
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    The impact of surface morphology on the magnetovolume transition in magnetocaloric LaFe11.8Si1.2
    (New York : American Institute of Physics, 2016) Waske, A.; Lovell, E.; Funk, A.; Sellschopp, K.; Rack, A.; Giebeler, L.; Gostin, P.F.; Fähler, S.; Cohen, L.F.
    First order magnetocaloric materials reach high entropy changes but at the same time exhibit hysteresis losses which depend on the sample’s microstructure. We use non-destructive 3D X-ray microtomography to understand the role of surface morphology for the magnetovolume transition of LaFe11.8Si1.2. The technique provides unique information on the spatial distribution of the volume change at the transition and its relationship with the surface morphology. Complementary Hall probe imaging confirms that on a morphologically complex surface minimization of strain energy dominates. Our findings sketch the way for a tailored surface morphology with low hysteresis without changing the underlying phase transition.
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    All-on-Chip Concurrent Measurements of the Static Magnetization and of the Electron Spin Resonance with Microcantilevers
    (Wien [u.a.] : Springer, 2021) Alfonsov, A.; Büchner, B.; Kataev, V.
    A large variety of the samples of novel magnetic materials, which are of high interest due to their exotic properties, are only available in very small sizes. In some cases, it is not possible to synthesize large single crystals; in other cases, the small size itself is the key prerequisite to manifest a specifically interesting property of the material. The smallness of a sample rises a problem of the detection of the static magnetic response and of the electron spin resonance (ESR) signal. To overcome this problem, we propose to use a cantilever-based (torque-detected) setup with the capability of a simultaneous measurement of ESR and static magnetization. This setup offers a high sensitivity and the ability to acquire along with the ESR signal the components of the magnetization tensor in a single experimental run. Here, we present the working principle of this setup, as well as the estimate of its sensitivity from the measurements on the standard Co Tutton salt sample. © 2021, The Author(s).
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    Spin-orbit coupling control of anisotropy, ground state and frustration in 5d2 Sr2MgOsO6
    (London : Nature Publishing Group, 2016) Morrow, Ryan; Taylor, Alice E.; Singh, D.J.; Xiong, Jie; Rodan, Steven; Wolter, A.U.B.; Wurmehl, Sabine; Büchner, Bernd; Stone, M.B.; Kolesnikov, A.I.; Aczel, Adam A.; Christianson, A.D.; Woodward, Patrick M.
    The influence of spin-orbit coupling (SOC) on the physical properties of the 5d2 system Sr2MgOsO6 is probed via a combination of magnetometry, specific heat measurements, elastic and inelastic neutron scattering, and density functional theory calculations. Although a significant degree of frustration is expected, we find that Sr2MgOsO6 orders in a type I antiferromagnetic structure at the remarkably high temperature of 108 K. The measurements presented allow for the first accurate quantification of the size of the magnetic moment in a 5d2 system of 0.60(2) μB –a significantly reduced moment from the expected value for such a system. Furthermore, significant anisotropy is identified via a spin excitation gap, and we confirm by first principles calculations that SOC not only provides the magnetocrystalline anisotropy, but also plays a crucial role in determining both the ground state magnetic order and the size of the local moment in this compound. Through comparison to Sr2ScOsO6, it is demonstrated that SOC-induced anisotropy has the ability to relieve frustration in 5d2 systems relative to their 5d3 counterparts, providing an explanation of the high TN found in Sr2MgOsO6.