Chemical Pressure Effect On The Structure And Ferromagnetism Of Diluted Magnetic Semiconductor (La,Ca)(Zn,Mn) AsO

Diluted magnetic semiconductors(DMS)use the charge and spin properties of electrons at the same time,which integrates the properties of magnetism and semiconductors.The rich magneto-optic and magneto-electric properties make it a promising application in the field of spintronic devices.At the end of the 20th century,thanks to the development of low-temperature molecular beam epitaxy(LT-MBE),researchers have successively prepared(Ga,Mn)As,(In,Mn)As and other III-V thin film DMSs,among which(Ga,Mn)As has the Curie temperature(TC)of 200 K.The realization of spin injection in semiconductors has attracted widespread attention in the field of DMSs.Subsequently,the discovery of Li(Zn,Mn)As bulk form DMS,realizing the separation injection of carriers and spins compared with the traditional III-V DMSs,expands the design ideas of DMSs.On this basis,a series of“111”type,“122”type,and“1111”type DMSs have been developed,among which the Curie temperature of“122”type(Ba,K)(Zn,Mn)2As2 reached 230 K,exceeding the record of 200 K for(Ga,Mn)As.However,the realization of DMSs available at room temperature still needs further exploration.Of course,exploring the dilute magnetic semiconductor materials whose Curie temperature is above room temperature is still one of the present day cutting-edge research topics.In recent years,the research about the modulation effect of pressure on the properties of DMSs has been widely carried out.The related research shows that pressure has an effective modulating effect on TC,which is an important means to further increase TC and to understand the magnetic origin mechanism of DMSs.This paper mainly conducts the following two aspects of research:(1)The investigation of chemical pressure effect on structure and ferromagnetic of dilute magnetic semiconductor(La,Ca)(Zn,Mn)AsO.Through Sb/As,Y/La substitution,we successfully prepared Sb-doped(La0.9Ca0.1)(Zn0.9Mn0.1)(As1-xSbx)O(x=0,0.05,0.10,0.15,0.20)and Y-doped(La0.9-yCa0.1Yy)(Zn0.9Mn0.1)AsO(y=0,0.025,0.05,0.075)polycrystalline samples.The monotonic changes of the lattice parameters a,c and the unit cell volume V indicate that the substitution of Sb/As and Y/La does introduce negative and positive chemical pressures into the diluted magnetic semiconductor(La,Ca)(Zn,Mn)AsO,respectively.Magnetic measurements show that TC of the sample changes in the opposite trend after applying negative and positive chemical pressures.And it is worth noting that the TC of the 7.5%Y-doped sample has increased by 30.7%compared with(La,Ca)(Zn,Mn)AsO.(2)Attempts and explorations of other novel dilute magnetic semiconductor materials.We prepared(La,Ba)(Zn,Mn)SbO,(Sr,M)F(Cu,Mn)Se(M=K,Na),Ag2(Zn,Mn)(Sn,Al)S4 polycrystalline samples,and characterize their structure and magnetic properties.