极性金属间化合物CaMn2Sb2和SrMn2Sb2中异常的锰-锰自旋耦合

Unusual Mn-Mn spin coupling in the polar intermetallic compounds CaMn2Sb2 and SrMn2Sb2.

作者信息

Bobev Svilen, Merz Justin, Lima Ana, Fritsch Veronika, Thompson Joe D, Sarrao John L, Gillessen Michael, Dronskowski Richard

机构信息

Department of Chemistry, University of Delaware, Newark, Delaware 19716, USA.

出版信息

Inorg Chem. 2006 May 15;45(10):4047-54. doi: 10.1021/ic060092e.

DOI:10.1021/ic060092e

PMID:16676965

Abstract

Large single-crystals of two polar intermetallic phases, CaMn2Sb2 and SrMn2Sb2, have been grown using In or Sn as metal fluxes and characterized by single-crystal X-ray diffraction. The two compounds are isostructural and crystallize with the CaAl2Si2 structure (space group P3m1, No. 164) with unit cell parameters determined at 120(2) K of a = 4.5204(6) angstroms, c = 7.456(2) angstroms and a = 4.5802(17) angstroms, c = 7.730(5) angstroms for CaMn2Sb2 and SrMn2Sb2, respectively. Temperature- and field-dependent dc- and ac-magnetization measurements suggest complex magnetic ordering of the Mn moments below ca. 250 and 35 K for CaMn2Sb2 and below ca. 265 K for SrMn2Sb2. Resistivity measurements reveal metallic-like temperature dependence with rho(290) = 40 m omega cm for CaMn2Sb2 and rho290 = 100 m omega cm for SrMn2Sb2 with negligible magnetoresistance at 5 K in applied magnetic fields up to 10 kOe. Spin-polarized DFT electronic structure calculations confirm the metallic-like properties and provide further evidence for a magnetic structure where Mn atoms form two magnetic sublattices with ferromagnetic coupling within them and strong antiferromagnetic coupling between them.

摘要

使用铟或锡作为金属助熔剂生长出了两种极性金属间化合物CaMn₂Sb₂和SrMn₂Sb₂的大单晶，并通过单晶X射线衍射对其进行了表征。这两种化合物具有相同的晶体结构，以CaAl₂Si₂结构（空间群P3m1，编号164）结晶，在120(2)K下测定的CaMn₂Sb₂和SrMn₂Sb₂的晶胞参数分别为a = 4.5204(6)埃，c = 7.456(2)埃和a = 4.5802(17)埃，c = 7.730(5)埃。温度和磁场依赖的直流和交流磁化率测量表明，对于CaMn₂Sb₂，在约250K和35K以下，以及对于SrMn₂Sb₂在约265K以下，Mn磁矩存在复杂的磁有序。电阻率测量揭示了类似金属的温度依赖性，CaMn₂Sb₂的ρ(290) = 40 mΩ·cm，SrMn₂Sb₂的ρ290 = 100 mΩ·cm，在高达10 kOe的外加磁场中，5K时的磁阻可忽略不计。自旋极化密度泛函理论（DFT）电子结构计算证实了类似金属的性质，并为一种磁结构提供了进一步的证据，其中Mn原子形成两个磁亚晶格，它们内部具有铁磁耦合，而它们之间具有强反铁磁耦合。