Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany and Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany.
Phys Rev Lett. 2014 Apr 11;112(14):147202. doi: 10.1103/PhysRevLett.112.147202. Epub 2014 Apr 10.
Magnetic properties and spin dynamics have been studied for the structurally ordered double perovskite Sr2CoOsO6. Neutron diffraction, muon-spin relaxation, and ac-susceptibility measurements reveal two antiferromagnetic (AFM) phases on cooling from room temperature down to 2 K. In the first AFM phase, with transition temperature TN1=108 K, cobalt (3d7, S=3/2) and osmium (5d2, S=1) moments fluctuate dynamically, while their average effective moments undergo long-range order. In the second AFM phase below TN2=67 K, cobalt moments first become frozen and induce a noncollinear spin-canted AFM state, while dynamically fluctuating osmium moments are later frozen into a randomly canted state at T≈5 K. Ab initio calculations indicate that the effective exchange coupling between cobalt and osmium sites is rather weak, so that cobalt and osmium sublattices exhibit different ground states and spin dynamics, making Sr2CoOsO6 distinct from previously reported double-perovskite compounds.
对结构有序的双钙钛矿 Sr2CoOsO6 的磁性和自旋动力学进行了研究。中子衍射、μ子自旋弛豫和交流磁化率测量表明，在从室温冷却到 2 K 的过程中存在两个反铁磁 (AFM) 相。在第一个 AFM 相中，转变温度 TN1=108 K，钴 (3d7，S=3/2) 和锇 (5d2，S=1) 磁矩动态波动，而它们的平均有效磁矩经历长程有序。在低于 TN2=67 K 的第二个 AFM 相中，钴磁矩首先被冻结，并诱导出非共线自旋倾斜 AFM 态，而动态波动的锇磁矩随后在 T≈5 K 时被冻结成随机倾斜态。从头算计算表明，钴和锇位点之间的有效交换耦合相当弱，因此钴和锇亚晶格表现出不同的基态和自旋动力学，使得 Sr2CoOsO6 与之前报道的双钙钛矿化合物明显不同。
