| Doped semiconductor and ferroelectrics are the hot topics in the field of spintronics and multiferroelectrics in which researchers are trying to developing new semiconductors and ferroelectrics. Lithium Niobate (LN) has extensive application in nonlinear optics and surface acoustic wave devices. LN, which has the similar optical band gap as GaN and ZnO, is believed to be optical silicon. Therefore, research on doped LN is of great scientific and practical value.In this paper, layered room temperature ferromagnetic Mn/Co doped LN were prepared by ion implantation. The doping concentration, recovery annealing, substrate oriention and doping elements were studied to reveal their influences on local structure and magnetic property of ferroelectric congruent single-crystal LN.Mn: LN of different doping concentration (atomic percentage) were prepared. Mn substituted Li in the lattice, which was confirmed by X-ray absortption near-edge spetrum and caculation based on Multi-Scattering (MS) and First Principle, but moved 0.10(A|°) along c axis. AGM tests showed that Mn: LN exhibited ferromagnetism at room temperature. The saturated magnetic moment (Ms) in Mn: LN at room temperature was 2.94μB/Mn, 2.65μB/Mn, 5.20μB/Mn, 0.69μB/Mn and 0.84μB/Mn when the doping amount of Mn was 1%, 2%, 3%, 4% and 5%, respectively. Among the different oriented substrates, (104) exhibited the most significant ferromagnetism and the Ms ratio of (104):(012):(001) is 1:0.25:0.1.Co: LN of 2%, 3.5% and 5% were prepared. XANES and First Priciple Caculation were applied to infer that Co ions went into Nb site of the lattice. VSM and MPMS were applied to charactize magnetic property of the samples. The atomic magnetic moment (AMM) in Co(3.5%,5%): (104)LN at room temperature was observed by MPMS to be 0.5μB/Co,0.24μB/Co while those of Co(2%): (104)/(006) by VSM are 1.0μB/Co,0.64μB/Co, respectively. Vacuum annealing at 200°C, 3.0×10-4Pa enhanced AMM of the samples, among which single energy implanted Co(3.5%): LN reached 4.9μB/Co.The results showed that Mn/Co doped LiNbO3 prepared by high-energy ion implantation in the range of concentration in this study were room temperature diluted ferromagnetic insulators. First Principle calculation and phenomenological model were applied to understand the room temperature ferromagnetism of the doped LiNbO3. |
