6533b853fe1ef96bd12ac09c

RESEARCH PRODUCT

Microscopic origin of magnetic anisotropy in martensitic Ni2MnGa

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The microscopic origin of magnetic anisotropy in the shape memory alloy Ni${}_{2}$MnGa is investigated by means of x-ray magnetic circular dichroism in transmission mode. Field- and angle-dependent dichroism spectra of epitaxial Ni${}_{2}$MnGa(101)/MgO(001) films reveal pronounced differences for magnetization aligned parallel and perpendicular to the film plane. These differences are related to an anisotropy of the orbital magnetic moment in agreement with the observed out-of-plane magnetocrystalline anisotropy. The spectral variation of the x-ray absorption originates from changes in the spin-projected density of states when the magnetization vector is rotated from the easy to the hard magnetic axis. Minority Ni states with ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ symmetry close to the Fermi energy form a wide half filled band for easy axis magnetization. When the magnetization is rotated into the hard axis the band narrowing of these states causes an increase of the mean kinetic energy of the electronic system. The opposite behavior of mostly unoccupied Ni states with ${d}_{\mathit{xy}}$ symmetry leads to an increase of the minority orbital moment for hard-axis magnetization.