Superexchange induced canted ferromagnetism in dilute magnets

Abstract

We argue, in contrast to recent studies, that the antiferromagnetic superexchange coupling between nearest neighbour spins does not fully destroy the ferromagnetism in dilute magnets with long-ranged ferromagnetic couplings. Above a critical coupling, we find a canted ferromagnetic phase with unsaturated moment. We have calculated the transition temperature using a simplified local Random Phase Approximation procedure which accounts for the canting. For the dilute magnetic semiconductors, such as GaMnAs, using ab-initio couplings allows us to predict the existence of a canted phase and provide an explanation to the apparent contradictions observed in experimental measurements. Finally, we have compared with previous studies that used RKKY couplings and reported non-ferromagnetic state when the superexchange is too strong. Even in this case the ferromagnetism should remain essentially stable in the form of a canted phase.

Magnetism, conductivity, and orbital order in(LaMnO3)2n/(SrMnODong1, Yu2, Yunoki3 et al. 2008Phys. Rev. B9631081View full textAdd to dashboardCite

“…Each ǫ i will be determined by its eight NN A-site cation neighbors. 16 More specifically, in the LMO-SMO superlattices, ǫ i is 0 for those Mn between two LaO planes (LMO region), it becomes V /2 for those between LaO and SrO planes, and finally it is V for those between two SrO planes (SMO region) ( Fig. 1(a-b)).…”

Half-metallicity, magnetism and electrical resistivity of Sn1−xMnxTe alloys in rock salt and zinc blende structures

“…For the FM phase the calculation of T c for such small concentration of the magnetic atoms, definitely below the percolation threshold, is difficult and cannot be carried out using VCA-RPA [39][40][41]. Perhaps methods based on random RPA including the effect of inhomogeneities [43][44][45]. Nadolny et al [3] find that for very low Mn-doping case (x r 0:04) in Mn 0.875 Sn 0.125 Te the specimens show FM behavior with T c r 6 K only if they are subjected to extra Te-flux.…”

Effects of vacancy and Na doping on the structural, magnetic and transport properties of La0.8Pb0.1(□/Na)0.1MnO3

“…Correlated disorder implies that when disorder is introduced, its effect is distributed in the bulk of the system. Recent model approaches [43] incorporating the effects of correlated disorder show that GP characteristics are enhanced.…”

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