TEMPERATURE INDUCED FERRO-ANTIFERROMAGNETIC TRANSITIONS IN EXCHANGE-COUPLED DOUBLE LAYERS WITH MIXED ANISOTROPIES

抄録

  The temperature dependence of the magnetization processes in mixed exchange-coupled double layers ECDL with a planar GdFeCo film 1 and a perpendicular anisotropy DyFeCo film 2 is analyzed from Faraday rotation measurements. During heating the magnetic state of the ECDL presents strong modifications depending not only on the external field applied along the normal to the layers, but mainly on the ECDL type which can change from a type 1 with an interlayer macroscopic antiferromagnetic (AF) coupling -A₁₂M₁.M₂ to a type 2 with a ferromagnetic (F) coupling. From appropriate choice of the deposition parameters the films compositions were adjusted for either T_cp1<RT<T_cp2 or RT<T_cp2<T_cp1 where T_cp1,2 are the compensation temperatures of the layer 1 and 2 which gives the possibility to obtain at RT ECDL of type 1/AF or type 2/F respectively. Depending on the respective values of T_cp1 and T_cp2, it is observed by increasing the temperature, F→AF or AF→F type transitions at T_cp1 and T_cp2. The evolutions with the temperature of the magnetooptical (MO) hysteresis loops of the ECDL are explained at the first order from the parallel change of the individual loops of the layers 1 and 2. However very close to T_cp2 more complex MO loops are observed and can be explained from the rise of the hysteresis H_c1 in the planar layer 1 induced by a strong increase of the coercitivity H_c2 of the perpendicular layer 2 near its compensation temperature.