Magnetic properties and magnetization reversal of CoSm‖Cr thin films

Abstract In this paper the magnetic and structural properties of CoSm thin films with a Cr underlayer (CoSm‖Cr) are presented, with emphasis on the measurements of anisotropy at room and low temperature and magnetization reversal. The grain size of the Cr underlayer is about 250 A and the thin CoSm layer (e.g., 240 A) inherits this grain size. The CoSm layer consists of nanocrystallites, about 50 A in diameter, embedded in an amorphous matrix. The Ar pressure, CoSm layer-thickness, and temperature dependencies of magnetic properties including magnetization, coercivity and especially the anisotropy were investigated systematically. CoSm‖Cr with coercivity up to 4.2 kOe at room temperature has been prepared. The intrinsic anisotropy is 4 × 10 6 and 1.4 × 10 7 erg/cm 3 at room temperature for CoSm(240 A)‖Cr and CoSm(960 A)‖Cr, respectively, and both increase to 3.9 × 10 7 erg/cm 3 at 10 K. Magnetization reversal studies indicate that the coercivity mechanism changes from wall pinning for samples prepared at lower Ar pressure (5–12 mT) to single-particle coherent rotation for samples prepared at higher pressure (30 mT). The correlations between the microstructure and magnetic properties are discussed.