Effect Of Li Doping On Structural And Magnetic Properties Of Sn TMO₂（TM=Fe, Ni, Mn, Cr, Co） Diluted Magnetic Semiconductors

Sn O2 is a wide-gap paramagnetic semiconductor at room temperature, with a typical gap size of ~ 3.6 e V, thus being ideal for serving as the host for diluted magnetic semiconductors(DMSs). Since Ogale et al found Co doped Sn O2 was ferromagnetic with giant moment of ~7.5 μB/Co, a huge amount of researches on Sn O2 based diluted magnetic semiconductors have been done. However, few Sn O2 based diluted magnetic semiconductors with a giant magnetic moment were reported recently. In order to enhance the magnetic moment of DMSs at the room temperature, IA elements were doped into oxide semiconductors aiming at influencing positively the ferromagnetic exchange interaction. Therefore, the giant magnetic moment at the room temperature is supposed to be essential property for the diluted magnetic semiconductors.In this paper, Li-doped Sn0.95-x(TM0.05,Lix)O2(0≤x≤0.08, TM=Fe, Ni, Mn, Cr, Co) were synthesized via conventional solid-state reaction. The structure of Sn0.95-x(TM0.05,Lix)O2 were carried out by an X-ray diffractometer(XRD) with Cu Kα radiation(λ=1.5418 ?) in the 2θ range from 20 o to 80 o. The dc magnetic susceptibility was measured at low temperature(2, 5 or 10 K) and room temperature(300 K) with the presence of a 10 k Oe magnetic field under both zero-field-cooling and zero-cooling conditions, on a magnetic property measurement system, Quantum Design. Isothermal magnetizations(M(H)) at low temperature(2, 5 or 10 K) and room temperature(300 K) were also measured on the same apparatus with the magnetic field within ±50 k Oe. To avoid the shielding of magnetization, loose powder of each sample was used for the measurement.Structure analysis based on powder X-ray diffraction revealed that all the samples present a rutile Sn O2 phase, and some impurities can be detected within the range of resolution. In addition, Li can influence the parameters a and c after its doping into Sn O2. Magnetic measurements revealed that Li doping indeed can enhance the magnetic moment of Sn0.95-x(TM0.05,Lix)O2 by inducing more carriers into Sn O2 at low temperature. Carriers can be regarded as a medium among transition metal elements so that the magnetic exchange interaction between transition metal elements will increase to some extent. At room temperature, Sn0.95-x(TM0.05,Lix)O2 almost present the paramagnetism, indicating temperature increasing will influence negatively the magnetic exchange interaction between transition metal elements by disordering the domains direction of Sn0.95-x(TM0.05,Lix)O2(0≤x≤0.08, TM=Fe, Ni, Mn, Cr, Co).