Induced high-temperature ferromagnetism by structural phase transitions in strained antiferromagnetic γ-Fe50Mn50 epitaxial films

Abstract

Strain effects in epitaxial films can substantially enhance individual functional properties or induce properties which do not exist in corresponding bulk materials. The bcc α -Fe 50 Mn 50 films are a ferromagnetic with a Curie temperature between 650 K and 750 K, which do not exist in nature can be manipulated through the tensile strain. In this study, γ -Fe 50 Mn 50 epitaxial films grown on GaAs(001) using molecular beam epitaxy are found to structural transition from the face-centered-cubic (fcc, a = 0.327 nm) γ -phase to the body-centered-cubic (bcc, a = 0.889 nm) α -phase. For α -Fe 50 Mn 50 epitaxial films, ferromagnetism is accompanied by structural phase transition due to the tensile strain induced by the differences of the thermal expansion between the film and the substrate. Moreover, by realizing in epitaxial films with fcc structure a tensile strain state, phase transitions were introduced Fe-Mn alloy system with bcc structure. These findings are of fundamental importance to understanding the mechanism of phase transition and properties of epitaxial CuAu-I type antiferromagnetic alloy thin films under strain.

Structural, magnetic and magneto-optical studies of Mn/Al bilayer thin films on GaAs substrates

“…These tilted loops indicate the antiferromagnetic nature in the as-deposited and MnAl_300_1h lms; similar tilted loops were also observed in FeMn lms. 43 The antiferromagnetic nature could be due to the presence of the 3-phase, which is dominant in these samples, as conrmed by XRD and VSM results. Films annealed at higher temperatures (400 and 500 C) show nonrectangular in-plane ferromagnetic MOKE-hysteresis loops, which did not saturate, with a coercivity of 258 Oe and 557 Oe and maximum Kerr rotation of around 8 mdeg and 17 mdeg, respectively (see Fig.…”

Strain driven phase transition and mechanism for Fe/Ir(111) films

“…In terms of introducing heterogeneous interfaces, the stabilization of crystallographic phases is critical to a viable strategy for the development of new materials with novel characteristics 17 – 25 . For example, Fe 50 Mn 50 epitaxial films grown on GaAs(001) were found to undergo a structural transition from a face-centered-cubic (fcc) phase to a body-centered-cubic (bcc) phase which does not exist in nature 18 . For bcc-Fe 50 Mn 50 epitaxial films, the occurrence of ferromagnetism is accompanied by a structural phase transition due to the tensile strain at the interface 18 .…”

“…For example, Fe 50 Mn 50 epitaxial films grown on GaAs(001) were found to undergo a structural transition from a face-centered-cubic (fcc) phase to a body-centered-cubic (bcc) phase which does not exist in nature 18 . For bcc-Fe 50 Mn 50 epitaxial films, the occurrence of ferromagnetism is accompanied by a structural phase transition due to the tensile strain at the interface 18 . An anomalous enhancement in the total magnetic moment and changes in coercivity were previously reported for Ni x Ti 1−x /Ni and Ni x Ti 1−x /Co, changes that can be attributed to interfacial strain, as evidenced by the magnetoelastic coupling in these heterostructures 19 .…”