No abstract

The dependence of free layer coercivity on the angle between easy axis and applied magnetic field was studied on [Ta, (Ni80Fe20)60Cr40]/ Ni80Fe20/Co90Fe10/Cu/Co90Fe10/Mn75Ir25/Ta spin valves with various interlayer coupling. Sharp decrease on the angle was observed for ferromagnetically coupled spin valves. The coercivity was reduced down to tenth of Oersted without any decrease of GMR-effect by forming nearly parallel anisotropy configuration. The angles at which the transition from hysteretic to anhysteretic magnetic reversal takes place are detected by analyses of the angle dependence of coercivity. Interpretation of experimental data is based on Stoner-Wohlfarth coherent rotation approach.

The results of measurements of temperature and magnetic-field dependences of magnetization, resistivity, thermopower, and Hall effect in La 0.7 Ca 0.3 MnO 3 single crystal are reported. It is shown that below 220 K, the holes of low mobility dominate conductivity, so that the crystal behaves as a "bad" metal, which is at the threshold of localization at T = 220 K. Above 250 K, La 0.7 Ca 0.3 MnO 3 is in the paramagnetic semiconductor state with the nearest-neighbor hopping conductivity. The ferromagnetic-to-paramagnetic phase transition is first order; the transition heat is about 0.04 kJ/mol. Application of a magnetic field results in the shift of T C toward higher temperatures with the rate dT C / dH Ϸ 0.8 K/kOe. The shift in T C is the driving force for the colossal magnetoresistance ͑CMR͒ effect observed in La 0.7 Ca 0.3 MnO 3 .

No abstract

No abstract