Field-induced first-order antiferromagnetic-ferromagnetic transitions in RMn2Ge2 compounds and their relation to the magnetostriction of the Mn sublattice
Jhvj. Brabers et al., Field-induced first-order antiferromagnetic-ferromagnetic transitions in RMn2Ge2 compounds and their relation to the magnetostriction of the Mn sublattice, PHYS REV B, 59(14), 1999, pp. 9314-9323
A model for field-induced first-order antiferromagnetic-ferromagnetic trans
itions is presented. The model is based on a free-energy expression includi
ng Mn-Mn and R-Mn exchange interactions, as well as harmonic and anharmonic
contributions to the lattice deformation energy. The Mn-Mn interaction is
assumed to be linearly dependent on the unit-cell dimensions, giving rise t
o magnetostrictive phenomena. The magnetostriction appears to be crucial fo
r the occurrence of the first-order antiferromagnetic-ferromagnetic transit
ions. From the model, an expression for the critical field B-c, correspondi
ng to the first-order transition, has been obtained and used for a descript
ion of the temperature dependence of B-c. The model is tested experimentall
y by magnetization measurements on several Sm1-yRyMn2Ge2 compounds and appe
ars to give a good description of the measured B-c vs T relations. Implicat
ions of the present work for magnetoresistance in bulk compounds and thin f
ilms are briefly discussed. [S0163-1829(99)13113-8].