Epitaxial growth of highly coercive Sm–Co thin films using pulsed laser deposition

Abstract

Hard magnetic materials with a uniaxial magnetocrystalline anisotropy can be most efficiently used if the easy axis is well aligned along one crystallographic direction in the entire sample volume. Epitaxial growth is one suitable method to achieve this aim and therefore Sm–Co thin films on Cr-buffered single-crystal MgO (100) substrates were deposited. Pulsed laser deposition from elemental Sm and Co targets was used to prepare films of nominal Sm2Co7 stoichiometry. Pole figure measurements and magnetization measurements reveal an epitaxial growth of Cr on MgO onto which the c axis of the Sm–Co layer is aligned in plane, viz., MgO(001)[100]‖Cr(001)[110]‖Sm–Co(110)[001]. At higher deposition temperatures an additional Sm–Co (1 1 16) texture was observed. This corresponds to an additional epitaxial orientation relation, where the c axis is tilted 60° out of the substrate plane. However, at low deposition temperatures and with smaller pulse repetition rates a reduction in the amount of this unwanted component can be achieved. This leads to the orientation of the c axis, which is the easy magnetization axis, only along two equivalent MgO [100] directions in the substrate plane. The resulting magnetic anisotropy has been confirmed by hysteresis measurements along three nonequivalent directions where high remanences and a high coercivity of up to 2.4T along MgO [110] can be achieved.