First-principles study of the magnetic stability and the exchange couplings of LaMn2O5

Abstract:

Using first principles calculations, the electronic and magnetic properties of the multiferroic

LaMn2O5 have been studied. In particular, we have studied the magnetic stability of this material

not only in ab-plane but also along c direction. Beside this, the exchange couplings between

manganese ions have been calculated using Heisenberg model by including only the nearest

neighbour interactions. It is shown that the stable magnetic order of LaMn2O5 is of

antiferromagnetic type, which is in good agreement with the experiments. In order to show the

effect of the temperature on the properties of our compound we have carried out this study using

two crystal structures: the higher symmetric one (space group Pbam) that reported

experimentally at T(98.8 k) and the lower symmetric one (space group Pmc21) that obtained

from the relaxation, in our calculations, at T¼0K starting from the stable magnetic order.This

structure deformation at T¼0 can be related to the exchange coupling striction. The density of

states show an insulating behavior in the antiferromagnetic state of LaMn2O5 at Fermi level and

there is a small band gap, confirming the experimental fact that LaMn2O5 is an insulator. We

have found that the nature of the mechanism of these magnetic exchange coupling is an indirect

super-exchange.

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https://www.academia.edu/19560829/First-principles_study_of_the_magnetic_stability_and_the_exchange_couplings_of_LaMn_sub_2_O_sub_5_