Effect of support on structural and magnetic properties of thin FeRh/MgO films

JIMÉNEZ, M. J.; CABEZA, G. F.

Santa Fé

Conferencia; VI San Luis School and Conference on Surfaces, Interfaces and Catalysis; 2018

Universidad Nacional del Litoral

The iron-rhodium (FeRh) alloy is known to have a first-order magnetic transition from the antiferromagnetic (AFM) to the ferromagnetic (FM) state as the temperature is increased to around 50 or 60 K above room temperature1. This alloy is of technological interest for the manufacture of new devices for magnetic storage2.Experimentally, FeRh films are deposited on substrates like MgO, Al2O3, sapphire or silicon. At present, it has been observed that FeRh films grown onto c-axis sapphire exhibits a lower transition temperature than the one grown onto MgO since tensile in-plane strain favors the FM over the AFM state3. Another important experimental result is that the AFM phase becomes increasingly unstable as the thickness of the film decreases4. Obviously both type of substrate and the thickness of the film are very important parameters to take into account. In this work, we investigate the effect of the support (MgO) in the structural and magnetic properties of FeRh thin films by performing density functional theory (DFT) electronic structure calculations using the VASP5 code. Both systems have been modeled using supercells. In the case of isolated films, the slab consists of 5 monolayers (ML) of FeRh with each monolayer consisting of Fe or Rh atoms depending on whether the surface terminates in Fe or Rh. In the case of the film supported on the top of a MgO slab, a substrate consisting of 3 ML of MgO and the same number of layers of FeRh was considered. The analysis of the results shows that the supported Rh-terminated surfaces undergo greater relaxations/contractions than the Fe-terminated ones. Comparing both Fe- and Rh- terminations for isolated and supported films the Fe-terminated system is slightly more stable than the same terminated in Rh in all cases. Finally, the effect of the support on the magnetic moment (mm) of the atoms can be mentioned. In the case of the Rh-terminated surface, the mm of the all Rh atoms decrease unlike those of the Fe that increase. On the other hand, when the Fe-terminated surfaces are considerer, all mm are increased except for the Fe atoms in contact with the substrate, observing an increase in the average magnetization of the MgO.