Phase Competition And Self Exchange Bias In FePt₃

This paper have investigated the influence of the chemical order to the magnetic structure and magnetic properties of FePt₃.The relation of the phases of FePt₃ at different chemical order and exchange bias phenomenon have been studied from theoretical calculation and experiment.The main results of this paper are as follows:?1?Super-cell model have been established and we have got different chemical order FePt₃ by switching the site of atoms.The results of energy and magnetic moment of FePt₃ three phases at different chemical order have been got by theoretical calculation and from it we can discover that: The most stable phase is AFMQ1 for completely ordered FePt₃ and the energy difference between AFMQ1 and AFMQ2 phases is smaller as chemical order decrease.Whether it is the stoichiometric ratio of FePt₃ or Pt-rich FePt₃,the introduction of chemical disorder can induce the appearance of AFMQ2 phase,just the the latter is more difficult.Similarly,the magnetic moment is 0 at completely ordered FePt₃ but net magnetic moment exists when the chemical order decrease.From above theoretical calculated results we can conclude that the introduction of chemical disorder can induce AFMQ2 phase.?2?The FePt₃ films have been fabricated by Magnetron sputter and PLD at the different temperatures and have been characterized by XRD.The chemical of films have calculated by Lorentz fitting.The results of XRD indicate that all the samples are single crystal.By calculating the chemical order,we can conclude that the higher preparative temperature,the higher the degree of chemical order.So the fabricated temperature affect the degree of chemical order by influence the mobility of atoms.?3?The magnetic properties of FePt₃ sample at different temperatures have been measured by VSM and the dependence of exchange bias on temperature has investigated.It was found that the exchange bias show different temperature dependence in different temperature ranges,suggesting AFMQ2 phase may appear in the films.Based on the theoretical results we obtained,the appearance of Q2 phase may be induced by the disordering of FePt₃.Our study suggests that competition between AFMQ1 and AFMQ2 exists in partially ordered FePt₃,and the chemical disorder may induce the appearance of AFMQ2 phase.