Magnetic structure of 3d-element doped Mn4N films confirmed by X-ray magnetic circular dichroism – Conditions for magnetic compensation

Abstract

We investigated the magnetic structure of Mn4N epitaxial films doped with 3d elements and discussed conditions under which magnetization compensation (MC) occurs in these films at room temperature. Three examples are discussed here: Co-doped Mn4N, Fe-doped Mn4N, and Cr-doped Mn4N epitaxial films grown on SrTiO3(001) substrates. Mn4N is a ferrimagnet with an antiperovskite structure composed of two sublattices with their magnetizations aligned antiparallel to each other: Mn atoms at corner sites, Mn(I) atoms; and Mn atoms at face-centered sites, Mn(II) atoms. In a previous study, X-ray magnetic circular dichroism (XMCD) measurements revealed that Co atoms preferentially replaced Mn(I) atoms with their magnetic moments aligned antiparallel to those of Mn(I) atoms, and that the MC occurred at two Co compositions in Mn4−xCoxN epitaxial films (x ≤ 1.3) at room temperature (RT). At x > 1.3, however, there was no MC composition at RT. In contrast, no such preferential occupations sites were observed for Fe in Mn4−yFeyN (y ≤ 1.2) or Cr in Mn4−zCrzN (z ≤ 1.5) epitaxial films, and the MC did not occur in these films at RT. As for Mn4−yFeyN epitaxial films, XMCD measurements indicated that Fe atoms substituted for not only Mn(I) but also Mn(II) atoms even when the Fe composition was small (y < 1). Similar results were obtained for Cr atoms in Mn4−zCrzN epitaxial films. On the basis of these results, we reached a conclusion that the difference in site selectivity has a strong impact on the presence or absence of the MC point in Mn4N.