Ni-substitution effect on the properties of Ba_(0.5)Sr_(1.5)Zn_(2-x)Ni_xFe_(12)O_(22) powders

摘要

We consider the influence of the magnetic cation (Ni~(2+)) substitution on the structural and magnetic properties of Ba_(0.5)Sr_(1.5)Zn_(2-x)Ni_xFe_(12)O_(22) (x = 0.8, 1, 1.5) powders. The powders were synthesized by using the citric-acid sol-gel auto-combustion method. Their ac-magnetization was measured in an ac-magnetic field with an amplitude of 10 Oe and a frequency of 1000 Hz to detect any magnetic phase transitions. A strong influence of the Ni-substitution on the magnetic properties was thus observed. A magnetic phase transition from a helicoidal to a ferrimagnetic spin order at 284 K was observed for the sample Ba_(0.5)Sr_(1.5)Zn_(0.5)Ni_(1.5)Fe_(12)O_(22). The magnetic-phase transition from conical spin order to hellicoidal spin order was registered at 149 K and 177 K for x = 0.8 and x = 1, respectively. Triple hysteresis loops were observed for all samples at 4.2 K, which indicates the presence of two kinds of ferromagnetic states with different magnetization values.