Neutron Powder Diffraction in mixed perovskites LuFe1-xCrxO3 with x= 0.25;0.45;0.55 and 0.75 to elucidate the magnetic structure and performed MonteCarlo simulations to reproduce the magnetic behavior

FLORENCIA LURGO; ORLANDO BILLONI; RAUL CARBONIO

Washington

Congreso; DXC- 69th Annual Denver X-Ray Conference; 2020

ICDD

In this work we studied the magnetic structure of the perovskite LuFe1-xCrxO3 (x= 0.25;0.45;0.55 and 0.75) family. The structural analysis was carried out by Neutron powder diffraction (NPD) with Rietveld analysis. NPD shown that the magnetic structure of this compound is Γ4 (GxAyFz) (Bertaut Notation) [1] in all the temperatures except the composition x=0.75 in 1K which is Γ4/ Γ2. In the Γ4 structure the moments are oriented mainly in antiferromagnetic (AFM) type-G arrangement along the crystallographic a-direction. A ferromagnetic component along c-axis (canted configuration) and an AFM type-A arrangement along b-axis are allowed by symmetry [2,3]. This canting is responsible to a weak ferromagnetic behavior (WFM) below the Neél temperature. In these compound the WFM can be due to two mechanisms related with two different magnetic interactions: antisymmetric exchange or Dzyaloshinskii?Moriya interaction (DM) and single-ion magnetocrystalline anisotropy. In orthocromites and orthoferrites the WFM is mainly for DM interactions [2]. In the present work we assume a simplified model for the DM interaction consistent with an AFM Gx arrangement and a ferromagnetic canting in the z direction (Fz) only. In our model the DM vectors are all oriented along the y direction and staggered in every direction. It is easy to see that such choice of the DM vectors orientations is consistent with the experimentally observed magnetic structure. We model the magnetic behavior of these perovskites using a Hamiltonian of classical Heisenberg spins lying in the nodes of a cubic lattice with N= (L x L x L) sites and comparing this results with experimental measurements to magnetic moment vs temperature