Surface effect on the magnetism of aMnPt3-type ordered surface alloy on Pt(001)

Abstract

We grow a $\mathrm{Mn}{\mathrm{Pt}}_{3}$-type trilayer ordered surface alloy on Pt(001), $c(2\ifmmode\times\else\texttimes\fi{}2)$ $\mathrm{Mn}\text{\ensuremath{-}}\mathrm{Pt}∕1\mathrm{ML}$ $\mathrm{Pt}∕c(2\ifmmode\times\else\texttimes\fi{}2)$ $\mathrm{Mn}\ensuremath{-}\mathrm{Pt}∕\mathrm{Pt}(001)$, of which atomic structure is investigated by dynamic low energy electron diffraction analysis. Magneto-optic Kerr effect measurements of the surface alloy at $45\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ show no hysteresis, although bulk $\mathrm{Mn}{\mathrm{Pt}}_{3}$ ordered alloy is ferromagnetic. Ab initio total energy calculations based on density functional theory, rather, predict that ferromagnetic order is not the ground state for the surface alloy. We propose that the nonferromagnetic order of the surface alloy originates mainly from surface effects in regards to nonferromagnetic ground state also found for the near-surface layers of the bulk-terminated $\mathrm{Mn}{\mathrm{Pt}}_{3}(001)$.