Synthesis And Characterization Of Novel Diluted Magnetic Semiconductors La(Zn_1-2xMn_xCu_x)AsO

Diluted magnetic semiconductors (DMSs) have the advantages of both ferromagnets and semiconductors, which will be very promising to fabricate spintronic devices. This dissertation first presents the investigations of III-V DMSs and new bulk form DMSs named as "111", "122", "1111", "32522", "42622" families. Compared to the traditional III-V DMSs, these new type DMSs have the advantage of decoupled charge and spin doping, which provides us a new way to investigate the DMS. Contrast to the thin film (Ga, Mn)As, these materials are in bulk form, which enables us to study the ferromagnetic mechanics with the microscopic probes, such as nuclear magnetic resonance (NMR), muon spin relaxation(μSR), and neutron scattering.We have successfully synthesized a new "1111" bulk form DMS La(Zn1-2xMnxCux)AsO, in which charge and spin are introduced by (Zn, Cu) and (Zn, Mn) substitution, respectively. The magnetization measurements indicate that magnetic ordering state can not be obtained only with (Zn, Mn) substitution. Only when Zn are substituted by both Mn and Cu simultaneously, can the system undergoes a magnetic order transition. The small saturation moment of La(Zn1-2xMnxCux)AsO is 0.01μB/Mn at 2 K and 100 Oe, implying spin glass state rather than long range ferromagnetic order.We have also tried substituting Zn with other transition metal elements to fabricate polycrystalline La(Zn1-2xMnxTMx)AsO (TM= Co, Fe, Ni). Unfortunately, ferromagnetic ordering state hasn’t been observed though magnetization measurements for these materials.