Magnetic phase stability of monolayers: Fe on Ta(x)W(1-x) (001) random alloy as a case study

TL;DR

This paper introduces a new method to analyze magnetic phase stability in monolayers on nonmagnetic substrates, applying it to Fe on Ta(x)W(1-x) alloys, revealing various magnetic ground states and transitions.

Contribution

A novel computational approach for studying magnetic phase stability that considers a wide range of magnetic configurations beyond traditional methods.

Findings

Crossover from ferromagnetic to antiferromagnetic ground state with substrate composition.

Potential existence of incommensurate magnetic structures at specific alloy compositions.

Broader applicability to complex magnetic systems beyond conventional energy calculations.

Abstract

We present a new approach to study the magnetic phase stability of magnetic overlayers on nonmagnetic substrates. The exchange integrals among magnetic atoms in the overlayer are estimated in the framework of the adiabatic approximation and used to construct the effective classical two-dimensional Heisenberg Hamiltonian. Its stability is then studied with respect to a large number of collinear and non-collinear magnetic arrangements which include, as special cases, not only ferromagnetic and various antiferromagnetic configurations, but also possible incommensurate spin-spiral structures. This allows us to investigate a broader class of systems than a conventional total energy search based on few, subjectively chosen configurations. As a case study we consider the Fe-monolayer on the random nonmagnetic bcc-Ta(x)W(1-x) (001) surface which was studied recently by a conventional approach. We have found a crossover of the ground state of the Fe monolayer from the ferromagnet on the Ta surface to the c(2x2) antiferromagnet on the W surface and that at the composition with about 20 % of Ta an incommensurate magnetic configuration might exist.