Torque analysis of Co-Cr films prepared under different Ar pressures

This paper describes the results of torque analysis on the Co-Cr 17-18at.% sputtered films prepared with the controlled Ar gas pressure (P-Ar) at 4-70 mTorr. At lower P-Ar (P-Ar<20mTorr), the Co-Cr films show, a higher coerciv e force (H-c) but a smaller magnetic anisotropy constant (K-n), The smaller K-n is considered to be due to the film shape anisotropy induced by surfac e magnetic charges on the film. The higher H-c is caused by the decrease of the exchange interaction between columnar Co grains with enhanced Cr segre gation at grain boundaries. Meanwhile at higher PU (20mTorr<P-Ar<70mTorr), the Co-Cr films show a lower H-c but a larger K-a The lower H-c is caused b y the granulation of Co sputtered particles. The rotational hysteresis inte gral R-k increases gradually from 0.4 to 1.0 with increasing Ar pressure un til P-Ar=20mTorr. The R-h(=0.4) of Co-Cr films at P-Ar=6mTorr suggests that the coherent rotation of magnetization occurs in the columnar Co grains. O n the other hand the Rk remains between 0.7 and 1.0 for Co-Cr films at P-Ar >20mTorr which indicates the occurrence of incoherent magnetization rotatio n.