7 research outputs found
Six-fold in-plane magnetic anisotropy in Co-implanted ZnO (0001)
Magnetic anisotropies of Co-implanted ZnO (0001) films grown on
single-crystalline Al2O3 (11-20) substrates have been studied by ferromagnetic
resonance (FMR) technique for different cobalt implantation doses. The FMR data
show that the easy and hard axes have a periodicity of 60 degrees in the film
plane, in agreement with the hexagonal structure of the ZnO films. This
six-fold in-plane magnetic anisotropy, which is observed for the first time in
ZnO-based diluted magnetic semiconductors, is attributed to the substitution of
cobalt on Zn sites in the ZnO structure, and a clear indication for long range
ferromagnetic ordering between substitutional cobalt ions in the
single-crystalline ZnO films.Comment: 7 pages, 4 figure
Endotaxial α-Fe Nanoparticles in the High-Fluence Iron-Implanted Single-Crystal MgO
In this work, we report on the endotaxial growth of α-Fe nanoparticles in the near-surface layer under high-fluence iron ion implantation of the single-crystal magnesium oxide substrate. Comprehensive Mössbauer effect and magnetometry studies show that the implanted sample reveals a pronounced ferromagnetic response even at room temperature, and the α-Fe nanoparticles serve as its main source. The broad band at ~1000 Oe in the X-band magnetic resonance spectra originates from the α-Fe fraction. It manifests the properties of the easy-plane system with the four-fold in-plane anisotropy. The last indicates that the α-Fe nanoparticles are coherently incorporated into the host MgO matrix
Ion-Beam Synthesis of Structure-Oriented Iron Nanoparticles in Single-Crystalline Rutile TiO<sub>2</sub>
Magnetic nanoparticles embedded into semiconductors have current perspectives for use in semiconducting spintronics. In this work, 40 keV Fe+ ions were implanted in high fluences of (0.5 ÷ 1.5) × 1017 ion/cm2 into an oxide semiconductor and single-crystalline TiO2 plates of rutile structure with (100) or (001) face orientations. Microstructure, elemental-phase composition, and magnetic properties of the Fe-ion-implanted TiO2 were studied by scanning and transmission electron microscopies (SEM and TEM), X-ray photoelectron (XPS) and Rutherford backscattering (RBS) spectroscopies, as well as vibrating-sample magnetometry (VSM). The high-fluence ion implantation results in the formation of magnetic nanoparticles of metallic iron beneath the irradiated surface of rutile. The induced ferromagnetism and observed two- or four-fold magnetic anisotropy are associated with the endotaxial growth of Fe nanoparticles oriented along the crystallographic axes of TiO2
High temperature ferromagnetism in Co-implanted rutile
We report on structural, magnetic and electronic properties of Co-implanted
TiO2 rutile single crystals for different implantation doses. Strong
ferromagnetism at room temperature and above is observed in TiO2 rutile plates
after cobalt ion implantation, with magnetic parameters depending on the cobalt
implantation dose. While the structural data indicate the presence of metallic
cobalt clusters, the multiplet structure of the Co L3 edge in the XAS spectra
gives clear evidence for a substitutional Co 2+ state. The detailed analysis of
the structural and magnetic properties indicates that there are two magnetic
phases in Co-implanted TiO2 plates. One is a ferromagnetic phase due to the
formation of long range ferromagnetic ordering between implanted magnetic
cobalt ions in the rutile phase, and the second one is a superparamagnetic
phase originates from the formation of metallic cobalt clusters in the
implanted region. Using x-ray resonant magnetic scattering, the element
specific magnetization of cobalt, oxygen and titanium in Co-implanted TiO2
single crystals are investigated. Magnetic dichroism was observed at the Co L
edges as well as at the O K edge. The interaction mechanism, which leads to
ferromagnetic ordering of substituted cobalt ions in the host matrix, is also
discussed.Comment: 19 pages, 16 figure
Dose dependence of ferromagnetism in Co-implanted ZnO
We have studied the structural, magnetic and electronic properties of
Co-implanted ZnO (0001) films grown on Al2O3 (1120) substrates for different
implantation doses and over a wide temperature range. Strong room temperature
ferromagnetism is observed with magnetic parameters depending on the cobalt
implantation dose. A detailed analysis of the structural and magnetic
properties indicates that there are two magnetic phases in Co-implanted ZnO
films. One is a ferromagnetic phase due to the formation of long range
ferromagnetic ordering between implanted magnetic cobalt ions in the ZnO layer,
the second one is a superparamagnetic phase, which occurs due to the formation
of metallic cobalt clusters in the Al2O3 substrate. Using x-ray resonant
magnetic scattering, the element specific magnetization of cobalt, oxygen and
Zn was investigated. Magnetic dichroism was observed at the Co L2,3 edges as
well as at the O K edge. In addition, the anomalous Hall effect is also
observed, supporting the intrinsic nature of ferromagnetism in Co-implanted ZnO
films.Comment: 9 pages, 11 figure