Structure and magnetic properties of Ni/Ti multilayers

We report a study of structure and magnetic properties of Ni/Ti multilayers with different modulation wavelength, 10 nm less than or equal to lambda less than or equal to 40 nm, and constant sublayers thickness ratio d(Ni)/d(Ti) = 1. Specimens were characterized with X-ray diffraction, vibrating sample magnetometer and torque meter in as-deposited state and in successive stages of isothermal annealing at 423 K. Hysteresis curves of as-deposited samples revealed the typical feature of ferromagnetic films with predominant shape anisotropy. During annealing very pronounced changes in the hysteresis loops were observed. An analysis of the loops indicates the occurrence of distinct changes in magnetic anisotropy of Ni sublayers: their effective shape anisotropy is drastically reduced due to a development of the perpendicular anisotropy and/or a modification of the microstructure. The effect can possibly be applied to achieve desirable variation of perpendicular anisotropy in multilayers which consist of Ni sublayers.