Temperature dependence of magnetic properties in epitaxial Cu/Ni/Cu/Si(111) measured by magneto-optical Kerr effect

We report on magneto-optical Kerr e!ect (MOKE) measurements performed in the range 4}300 K on "ve epitaxial Cu/Ni/Cu/Si (1 1 1) heterostructures, grown by UHV evaporation, with the Ni layer thickness d varying in the range between 30 and 10 As . In a previous work, we showed that, at room temperature, the magnetization lies preferentially in-plane for d*30 As while it switches out-of-plane when 15)d)25 As . In this work, we show that on further reducing the "lm thickness the magnetization undergoes a second reorientation transition. For d"10 As an in-plane magnetization is found with a coercive "eld which becomes negligible above 200 K. No orientation transition is observed as a function of temperature for any of the specimens analyzed. However, the estimated coercive "eld and the loop squareness decrease monotonically with increasing temperature.