In this paper,the structural and magnetic properties of Ni metal implanted TiO 2 single crystals are discussed.Ni nanocrystals (NCs) have been formed in TiO 2 after ion implantation.Their crystalline sizes were increased with increasing post-annealing temperature.Metallic Ni NCs inside the TiO 2 matrix are stable up to an annealing temperature of 1073 K.The Ni NCs forming inside TiO 2 are the major contribution of the measured ferromagnetism.
Fe ions of dose 8×10 16 cm-2 are implanted into a ZnO single crystal at 180 keV.Annealing at 1073 K leads to the formation of zinc ferrite (ZnFe 2 O 4),which is verified by synchrotron radiation X-ray diffraction (SR-XRD) and X-ray photoelectron spectroscopy (XPS).The crystallographically oriented ZnFe 2 O 4 is formed inside the ZnO with the orientation relationship of ZnFe 2 O 4 (111)//ZnO (0001).Superconducting quantum interference device (SQUID) measurements show that the as-implanted and post-annealing samples are both ferromagnetic at 5 K.The synthesized ZnFe 2 O 4 is superparamagnetic,with a blocking temperature (T B=25 K),indicated by zero field cooling and field cooling (ZFC/FC) measurements.
5-at% Mn-doped and undoped BaTiO 3 thin films have been grown under different oxygen partial pressures by Pulsed Laser Deposition (PLD) on platinum-coated sapphire substrates.X-ray diffraction (XRD) measurements for all the thin films reveal a similar polycrystalline single-phase perovskite structure.Ferroelectricity is observed in the Mn-doped and undoped BaTiO 3 thin films grown under relatively high oxygen partial pressure.Ferromagnetic coupling of the Mn dopant ions,on the other hand,is only seen in Mn-doped BaTiO 3 thin films prepared under low oxygen partial pressure in a wide temperature range from 5 K to 300 K,and is attributed to the enhanced exchange coupling between Mn dopants and electrons at oxygen vacancies.Our results show that the leakage current is decreased with the doped Mn,but increases the dielectric loss and decreases the dielectric constant,and the ferroelectricity is impaired.To produce ferromagnetism,oxygen vacancies are necessary,which unfortunately increase the leakage current.This confirms that the mutual interplay between the ferroelectricity and ferromagnetism can be tuned by exchange coupling of the doped-Mn and oxygen vacancies in the BaTiO 3 thin films.
This paper reports that the 150-keV Mn ions are implanted into GaN thin film grown on Al2O3 by metal-organic chemical vapour deposition.The X-ray diffraction reciprocal spacing mapping is applied to study the lattice parameter variation upon implantation and post-annealing.After implantation,a significant expansion is observed in the perpendicular direction.The lattice strain in perpendicular direction strongly depends on ion fluence and implantation geometry and can be partially relaxed by post-annealing.While in the parallel direction,the lattice parameter approximately keeps the same as the unimplanted GaN,which is independent of ion fluence,implantation geometry and post-annealing temperature.
