RESUMEN
We show experimental evidence of magnetization switching in a single (Ga,Mn)(As,P) semiconducting ferromagnetic layer, attributed to a strong reduction of the magnetization and the anisotropy due to current injection. The nucleation of magnetization reversal is found to occur even in the absence of a magnetic field and to be both anisotropic and stochastic. Our findings highlight a new mechanism of magnetization manipulation based on spin accumulation in a semiconductor material.
RESUMEN
Combining electron paramagnetic resonance, density functional theory, and positron annihilation spectroscopy (PAS), we identify the nitrogen interstitial defect in GaN. The isolated interstitial is unstable and transforms into a split interstitial configuration (N-N)(N). It is generated by particle irradiation with an introduction rate of a primary defect, pins the Fermi level at E(C)-1.0 eV for high fluences, and anneals out at 400 °C. The associated defect, the nitrogen vacancy, is observed by PAS only in the initial stage of irradiation.
RESUMEN
Intrinsic paramagnetic defects in â¼5 nm sized nanodiamonds, produced by various dynamic synthesis (DySND) techniques (detonation, shock-wave, pulsed laser ablation of solid carbon containing targets), have been studied by multi-frequency electron paramagnetic resonance (EPR). X-band (9-10 GHz) EPR spectra of DySND, in addition to the main intensive singlet Lorentzian-like EPR signal, reveal a low intensity doublet pattern within the half-field (HF) region (g â¼ 4). On transferring spectra to the Q-band (34 GHz) the shape of the HF pattern changes and splitting between doublet components is reduced from 10.4 to 2.6 mT. The HF patterns observed are attributed to the 'forbidden' ΔM(S) = 2 transitions between the Zeeman levels of some spin-triplet (S = 1) centers. The model of two triplet centers with g â¼ 2.003 and zero-field splitting parameters D(1) = 0.095 cm(-1) (TR1) and D(2) = 0.030 cm(-1) (TR2) satisfactorily describes experimental results at both microwave frequencies. The spin-triplet-type defects are observed in a wide variety of DySND samples irrespective of industrial supplier, cooling and carbon soot refinement methods, initial purity, disintegration, or subsequent targeted chemical modification. This indicates that the intrinsic defects with S = 1 in DySND systems are of universal origin.
RESUMEN
We report the observation of a paramagnetic interface defect in thermally oxidized porous n-type doped 4H-SiC/SiO(2). Based on its axial symmetry and resolved hyperfine interactions it is attributed to an sp(3) carbon dangling bond center situated at the SiC side of the interface. This center is electrically active and pins the Fermi level in the oxidized samples. No silicon related paramagnetic dangling bond centers are observed. The formation of dangling bond centers seems to be related to interstitial oxygen diffusion at the interface during the oxidation process.