MAGNETIC-PROPERTIES AND SPONTANEOUS MAGNETOSTRICTION OF A SM2CO7 SINGLE-CRYSTAL

The high-field magnetization and the lattice parameters of the interme tallic compound Sm2Co7 have been studied on single-crystal samples in a wide temperature range. The compound is a highly anisotropic ferroma gnet having mu(s) = 10.1mu(B)/f.u., T(c) = 670 K and uniaxial magnetic anisotropy above 68 K. Below 68 K, a spontaneous spin reorientation o f the axis-cone type occurs and the cone angle reaches 15-degrees at 4 .2 K. The Sm atoms on the quasicubic sites are considered to be respon sible for the spin reorientation. The magnetic ordering is accompanied by positive spontaneous magnetostrictive strains in the basal plane a nd along the c axis which reach at 5 K 2.1 x 10(-3) and 3.6 x 10(-3), respectively. That corresponds to a spontaneous volume magnetostrictio n 7.8 x 10(-3). The spin reorientation is accompanied by an additional negative volume anomaly -0.9 x 10(-3).