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The combined effect of the spin-transfer torque and circular Amperian field to the switching of the chiralities of the dual-vortex magnetization in multilayered Ni80Fe20/Cu/Co nanopillar elements (o\ = 100 nm) is investigated numerically. It is demonstrated that, by passing a current pulse through the nanopillar, the chirality of the Ni80Fe20 layer can be controllably switched while that of the fixed Co layer persists. Consequently, reliable toggle switching between bistable low- and high-MR states can be achieved by applying current pulses with appropriate amplitude, polarity, and duration. It is found that the magnetization dynamics after the onset of a current pulse includes the excitation of spin-wave eigenmodes and that the predominant process throughout is the precessional motion of the free-layer magnetization. A shift of the eigenfrequency is observed when the chirality of the free-layer vortex magnetization switches from parallel to antiparallel relative to that of the fixed layer. This frequency shift is attributed to dynamic magnetostatic coupling between the vortices. [ABSTRACT FROM AUTHOR]

Room temperature ferromagnetic Zn0.95Co0.05O thin films with (002) preferential orientation have been successfully deposited by pulsed laser deposition at different oxygen partial pressures on n-type (100) silicon substrate. A maximum saturation magnetization of 0.86 μB/Co was achieved at room temperature at 5 × 10-6 Torr oxygen partial pressure. HRTEM and XPS results indicate that the observed ferromagnetism is not due to metallic Co microclusters in the thin films. Oxygen vacancies in the films were detected from photoluminance characterization, which showed a significant effect on the ferromagnetic behavior. By changing the amount of oxygen vacancies through adjusting the oxygen partial pressure during deposition and post-deposition annealing, the ferromagnetic behavior of the thin films can be tuned significantly. This implies that the oxygen vacancies, which contribute to the bound magnetic polarons model and RKKY indirect interaction, are the likely cause of this ferromagnetism. [ABSTRACT FROM AUTHOR]

We investigated the effects of Fe doping and point defects (oxygen and tin vacancies, VO and VSn, respectively) on the ferromagnetism of SnO2 through first-principles calculations by using generalized gradient approximation + U under density functional theory. Calculation results show that Fe-doped SnO2 with VO or VSn exhibit long-range ordered ferromagnetism and Curie temperature above room temperature. The system has different magnetic properties with different doping modes, which are beneficial to the magnetic adjustment of dilute magnetic semiconductor (DMS). The double-exchange effects among the electrons of O–2p and Fe–3d states are the origin of ferromagnetism in Sn15FeO31. Similarly, ferromagnetism in Sn14FeO32 is derived from the double-exchange effects among the electrons of O–2p and Fe–3d states. These effects are produced by hole carriers after complexes form by Fe doping and VO or VSn. Simultaneously, Sn14FeO32 shows a half-metallic behavior, thus resulting in 100% conduction hole polarizability, which is highly beneficial to DMSs as a hole-injection source. Moreover, results also show that the decreased distance between Fe and vacancies (VO or VSn) lowers formation energy and thus increases the system stability. [ABSTRACT FROM AUTHOR]

By micromagnetic simulation, we investigated a double 360° domain walls system in two parallel nanowires. Two domain walls are coupled to each other via magnetostatic interaction. When a spin-polarized current is applied to only one nanowire or both nanowires with the same direction, the two domain walls propagate along nanowires together. The critical velocity of such system is obviously higher than that of a single 360° domain wall. The interaction between the two domain walls can be modeled as two bodies that connected by a spring, and we analyzed the coupling characteritics of the double 360° domain walls at last. [ABSTRACT FROM AUTHOR]

Ni0.5Zn0.5Fe2O4(NZFO) thin films grown on LaNiO3(LNO) buffered Si (100) substrates were prepared by chemical solution deposition. The sample annealed rapidly at 600°C in oxygen atmosphere. X-ray diffraction result showed that, the sample annealed in oxygen atmosphere is polycrystalline thin film. Field-emission scanning electron microscopy result revealed that the average grain size of the sample is about 20 nm. The magnetic measurement gave a typical value of the saturation magnetization of 0.767 emu/cm3. The chemical states and chemical composition of the film was also determined by X-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties and the magnetocaloric effect are presented for the perovskite-related oxide SrFe0.5Co0.5O3 prepared using electrochemical oxidation. SrFe0.5Co0.5O3 exhibits a second order paramagnetic–ferromagnetic transition close to room temperature (T C =330K). The maximal magnetic entropy change ΔS M Max , the maximal adiabatic temperature change ΔT ad and the refrigerant capacity are found to be equal to respectively 4.0J/kgK, 1.8K and 258J/kg while raising the B-field change from 0 to 5T. [Copyright &y& Elsevier]

Using two suitably designed thin film systems, the impact of metallic cobalt nanodots on the mechanism of ferromagnetism (FM) in ZnO thin films was studied. At a relatively higher oxygen partial pressure, Co nanodots embedded ZnO thin films no longer show FM, as compared to Co-doped ZnO dilute magnetic semiconductor (DMS). The structural and magnetic properties of these two systems support the hypothesis that (1) the FM of DMS thin films is due to bound magnetic polarons instead of cobalt nanoclusters and (2) the critical defect concentration is the key parameter which controls the FM properties in DMS thin films. [ABSTRACT FROM AUTHOR]

Using two suitably designed thin film systems, the impact of metallic cobalt nanodots on the mechanism of ferromagnetism (FM) in ZnO thin films was studied. At a relatively higher oxygen partial pressure, Co nanodots embedded ZnO thin films no longer show FM, as compared to Co-doped ZnO dilute magnetic semiconductor (DMS). The structural and magnetic properties of these two systems support the hypothesis that (1) the FM of DMS thin films is due to bound magnetic polarons instead of cobalt nanoclusters and (2) the critical defect concentration is the key parameter which controls the FM properties in DMS thin films. [ABSTRACT FROM AUTHOR]

The room-temperature weak ferromagnetism of amorphous HfAlOx thin films deposited by pulsed laser deposition on various substrates in oxygen-defective ambient is demonstrated. The magnetization is independent of film thickness, but depends on substrates and deposition temperatures. A magnetic moment of ∼0.26μB per HfAlOx f.u. is recorded for HfAlOx films deposited under optimized conditions [deposited at 600 °C on (001) sapphire in high vacuum]. It is argued that interfacial defects are one of the possible sources of the weak ferromagnetism. [ABSTRACT FROM AUTHOR]

ZnO:Co thin films with room-temperature ferromagnetism have been synthesized on (001) Si substrates by pulsed laser deposition using a Zn0.95Co0.05O ceramic target. Single-phase wurtzite thin films with (002) preferential orientation were grown at 450 °C in vacuum. There is no indication of Co nanocluster formation. However, copious edge dislocations appear to have formed during the film growth. A saturation magnetization of 1.04 μB/Co and a coercivity of 25 Oe were obtained at room temperature. In addition to O vacancies, the Zn interstitial induced by edge dislocations may also contribute to the ferromagnetic properties in this oxide-diluted magnetic semiconductor. [ABSTRACT FROM AUTHOR]

We investigated the effects of Fe doping and point defects (oxygen and tin vacancies, VO and VSn, respectively) on the ferromagnetism of SnO2 through first-principles calculations by using generalized gradient approximation + U under density functional theory. Calculation results show that Fe-doped SnO2 with VO or VSn exhibit long-range ordered ferromagnetism and Curie temperature above room temperature. The system has different magnetic properties with different doping modes, which are beneficial to the magnetic adjustment of dilute magnetic semiconductor (DMS). The double-exchange effects among the electrons of O–2p and Fe–3d states are the origin of ferromagnetism in Sn15FeO31. Similarly, ferromagnetism in Sn14FeO32 is derived from the double-exchange effects among the electrons of O–2p and Fe–3d states. These effects are produced by hole carriers after complexes form by Fe doping and VO or VSn. Simultaneously, Sn14FeO32 shows a half-metallic behavior, thus resulting in 100% conduction hole polarizability, which is highly beneficial to DMSs as a hole-injection source. Moreover, results also show that the decreased distance between Fe and vacancies (VO or VSn) lowers formation energy and thus increases the system stability. [ABSTRACT FROM AUTHOR]

A new diluted ferromagnetic semiconductor (Sr,Na)(Zn,Mn)2As2 is reported, in which charge and spin doping are decoupled via Sr/Na and Zn/Mn substitutions, respectively, being distinguished from classic (Ga,Mn)As, where charge and spin doping are simultaneously integrated. Different from the recently reported ferromagnetic (Ba,K)(Zn,Mn)2As2, this material crystallizes into the hexagonal CaAl2Si2 type structure. Ferromagnetism with a Curie temperature up to 20 K has been observed from magnetization. The muon spin relaxation measurements suggest that the exchange interaction between Mn moments of this new system could be different from the earlier diluted magnetic semiconductors (DMS) systems. This system provides an important means for studying ferromagnetism in DMS. [ABSTRACT FROM AUTHOR]

We report the discovery of a diluted magnetic semiconductor, Li(Zn,Mn)P, in which charge and spin are introduced independently via lithium off-stoichiometry and the isovalent substitution of Mn2+ for Zn2+, respectively. Isostructural to (Ga,Mn)As, Li(Zn,Mn)P was found to be a p-type ferromagnetic semiconductor with excess lithium providing charge doping. First-principles calculations indicate that excess Li is favored to partially occupy the Zn site, leading to hole doping. Ferromagnetism with Curie temperature up to 34 K is achieved while the system still shows semiconducting transport behavior. [ABSTRACT FROM AUTHOR]