FIELD-IMPRESSED ANISOTROPY OF SUSCEPTIBILITY IN IRON-TERBIUM THIN-FILMS

Two thin films of Fe1-xTbx where x = 0.17 and 0.23 are shown to exhibi t the effect of field-impressed anisotropy. After application of a dir ect field of 80 mT, which gives them an isothermal remanent magnetizat ion (IRM) in their plane, the anisotropy of initial susceptibility dif fers from that measured after the films have been tumble-demagnetized. By subtracting the susceptibility results of the tumble-demagnetized state from those obtained after the application of the 80 mT direct fi eld, it is shown that the effect of this field is to decrease the susc eptibility measured along the former applied field direction and to in crease the susceptibility at right angles to this. The effect is almos t certainly due to changes in domain alignment. Even though these film s contain many domains, the above results are similar to those previou sly obtained for single-domain gamma Fe2O3 and magnetite particles. Th e sense of the effect is opposite to that for multi-domain magnetite p articles where the susceptibility has been found to increase along the previously applied field direction.