Metamagnetic Transitions in La $$_{0.5}$$ 0.5 Pr $$_{0
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INTERMETALLIC RMn2 X2 compounds (R: rare earth; X: Si, Ge) exhibit a variety of temperature-induced magnetic phase transitions and order in diverse magnetic configurations as a result of the exchange interactions between the f and d electronic states. For this reason, these compounds have attracted particular attention and were thoroughly investigated for their magnetic properties.[1–3] RMn2 X2 crystallizes in the ThCr2 Si2 -type (space group I4/mmm) layered structure with a body-centered tetragonal unit cell with c and a as the long and short axes, respectively.[5,6] The layers are made up of R, T (T: transition metal), and X atomic planes in the layering sequence R T X T R along the c-axis. The atomic coordinates for R, T, and X atoms in this type of structure are given as 2a(0,0,0), 4d (0, 0.5, 0.25 and 0.5, 0, 0.25), and 4e(0,0,z and 0,0,-z) respectively. According to the results of neutron diffraction studies,[7–15] the magnetic structure is such that the moments in the Mn layers align parallel or antiparallel along the c-axis depending on the intralayer Mn-Mn spacing. The moments in adjacent Mn layers align parallel along the of about 300 K c-axis at a Curie temperature Tinter C (27 C) when a>0:406 nm, or antiparallel at a Ne´el of about 300 K (27 C) when a0:402 nm. ing occurs at Tintra N Recently we found that the critical lattice parameters which determine the type of the exchange interaction can be different for both RMn2 Ge2 and RMn2 Si2 systems.[3] This indicates that not only the atomic EYU¨P DUMAN is with the Department of Energy and Materials Engineering, Ankara University, 06380, Go¨lbas¸ı, Ankara, Turkey. Contact e-mail: [email protected] MEHMET ACET is with Experimentalphysik, Duisburg-Essen University, 47048 Duisburg, Germany. THORSTEN KRENKE is with ThyssenKrupp Electrical Steel, Kurt-Schumacher-Str. 95, 45881 Gelsenkirchen, Germany. BACHIR OULADDIAF and EMMANUAL SUARD are with the Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France. Manuscript submitted August 3, 2016. Article published online January 6, 2017 1512—VOLUME 48A, MARCH 2017
separation, but also the exchange interactions mediated by Si or Ge influence the nature of magnetic coupling of the Mn sublattice moment. Temperature-dependent magnetization measurements on La1x Rx Mn2 Si2 (R: Pr, Sm, Gd, Dy, and Er) have shown the presence of temperature-induced antiferromagnetic–ferromagnetic (FM) transitions, which can be sharp or run over a broad temperature range.[3] The broadening of the transition can be related to different orientations of the magnetic field on Mn ions in powder sample. However, the broadening is more clear for Dy and Er meaning that the magnetic interactions vary also with different rare earths on the microscopic scale.[3] Therefore, the magnetic transition can locally occur at different temperatures and give rise to the broadening of the transition. Additionally, the temperature-induced FM–AF transition temperature can be shifted to lower or higher temperature by changing the nominal composi
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