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Abstract Microscopic coexistence between weak ferromagnetism (WFM) and superconductivity (SC) in T b 0.47 Y 0.53 N i 2 11 B 2 C was investigated. Magnetization measurements indicate that antiferromagnetic (AFM), WFM and SC transitions occur in this material. Unpolarized neutron diffraction experiments revealed that the AFM order is best described by a longitudinal spin density wave with a propagation vector of q = 0.550 a ∗. Polarized neutron diffraction experiments further confirmed that the WFM order is originated in T b 0.47 Y 0.53 N i 2 11 B 2 C. [ABSTRACT FROM AUTHOR]

The antiferromagnet thickness dependence of the net training effect is studied in exchange-coupled CoFe/MnIr bilayers. The maximum net training effect is observed near the critical thickness of the antiferromagnetic layer. The easy-axis redistribution of the unpinned antiferromagneic grains is explained by the two cycles of ferromagnetic-resonance measurement. The linear relationship between the net training effect and rotational hysteresis loss directly confirms that the training effect in ferromagnetic/antiferromagnetic bilayers originates from the reorientation of the unpinned antiferromagnetic grains from initial alignment to the final random state during consecutive cycles of hysteresis loops measurement. [ABSTRACT FROM AUTHOR]

Nanostructured magnetic tunnel junction rings (MTJ) based on CoFeB free layer were fabricated to investigate the corresponding magnetization reversal processes. The dimensions of the MTJ rings were with outer diameter/linewidth of 1 μm/100 nm and 0.7μm/100 nm, respectively, in which the fabrication was carried out by a top-down technique in combination with electron beam lithography, ion-milling and etch-back processes. Double transition processes in magnetoresistance (MR) responses are observed in these nanostructured MTJ rings. With considering the surface roughness, an OOMMF simulation was employed to explore the magnetization evolution. The simulated hysteresis loops are consistent with the MR behaviors, unfolding that the magnetic switching process initiates from the forward to reversed onion states through an incomplete vortex state. This two-step switching behavior is reasonably assumed to be due to a pinning site resulting from the surface roughness in a region of the ring. In addition, a series of in situ magnetic force microscopy images extracted from nanostructured MTJ rings reveals the similar magnetization evolution with the simulated results. [ABSTRACT FROM AUTHOR]

The family of half-Heusler compounds offers a variety of half-metallic ferromagnetic materials. We have applied the Mössbauer spectroscopy to study the atomic order, local surroundings and hyperfine fields to several half-Heusler compounds. 121Sb Mössbauer study of the compound CoMnSb revealed the presence of two nonequivalent antimony positions in the elementary cell and enabled to identify the structure. 119mSn, 155Gd and 197Au Mössbauer spectroscopic studies were used to characterize the properties of ferromagnetic granular material based on the half-Heusler ferromagnet MnAuSn in the antiferromagnetic GdAuSn matrix. [ABSTRACT FROM AUTHOR]

The element-selected magnetic circular dichroism (MCD) between Gd core states is observed in the soft X-ray region (1150–1250 eV). The dichroism intensity for the transition from the 3d to 4f orbital of the Gd atomic state is very strong and reaches up to about 30% at 15 K. The temperature dependence of the MCD intensity shows a ferromagnetic phase around 50–80 K in addition to the room temperature ferromagnetic phase. Its X-ray absorption near edge structure is different from those of other Gd compounds. It seems to be related to the strength of the ferromagnetic behavior. [ABSTRACT FROM AUTHOR]

Microstructured magnetic tunnel junction ring with outer/inner diameter of 2/1 μm has been fabricated to investigate the angular dependence of magnetoresistance during magnetization reversal process. The minor loop of magnetoresistive curve reveals four distinct resistance levels associated with four magnetization configurations within the free layer throughout the magnetization reversal. The magnetoresistance decreases with increasing angle between applied external field and biasing direction, which is resulted from the relative alignment of total magnetization of pinned and free layer. An extra feature appeared in the minor loop when the external field is transverse to the biasing direction; this can be attributed to a vortex-pair formation/annihilation in the free layer. Furthermore, a series of schemes of magnetic configurations of pinned and free layers are illustrated to explain the routes of minor loops. [ABSTRACT FROM AUTHOR]

Angular dependence of Hex and Hc, and the critical angle behavior are measured in CoFe/MnIr bilayers annealed at 200°C and 340°C. The interfacial exchange coupling anisotropy and the antiferromagnet anisotropy at tAF < tAFcare estimated from the best fitting of angular dependence of Hex and Hc using Stoner-Wohlfarth (S-W) model. These results confirm existence of interfacial exchange coupling anisotropy between F and AF layers for tAF < tAFc. The measured critical angles for tAF > tAFc as well as for tAF < tAFc are well explained using S-W model. [ABSTRACT FROM AUTHOR]

We have measured the hysteresis loop and torque curves at various applied magnetic field angle in CoFe/MnIr epitaxial bilayers on single crystal MgO (001), (111), and (011) samples. The (001) samples show double shifted magnetization curves, which are dominant as the MnIr thickness increases. It suggests that the unidirectional anisotropy and cubic anisotropy of CoFe (001) layer plays a key role in the formation of double shifted magnetization reversal. The angular variation of exchange bias (Hex) and coercive field (Hc) depend on the orientation of MgO substrates. The measured results are compared with calculated data, which are fitted using the crystalline anisotropy, unidirectional and uniaxial anisotropy induced by the field annealing. The calculated Hex and He as a function of measuring angles show similar trend as the measured ones. Theses energy contributions play an essential role in the angle dependent magnetization process in epitaxial CoFe/MnIr bilayers. [ABSTRACT FROM AUTHOR]

This report investigates the current-induced switching of exchange bias without an external magnetic field in nano-scaled magnetic tunnel junction (MTJ) cells. An MTJ stack film was patterned into an ellipse with dimensions of 120 nm × 270 nm by using standard electron beam lithography in combination with ion beam etching. A spin-polarized current pulse with a duration of 100 ns was used to switch the exchange bias direction of the synthetic antiferromagnetic (SAF) pinned layer. It is worth noting that the MTJ cell was initialized in a high resistance state before applying the current pulse. For the application of both positive and negative current pulses, the resistance can be switched from the high (antiparallel) state to the low (parallel) one at 2.95 and -2.80 mA, respectively. After the current-induced switching, it was found that the magnetoresistance curve is reversed relative to the one before the current-induced switching. Predominantly, this behavior is independent of the polarity of the current pulse. As a result, it is shown that the exchange bias in the SAF pinned layer changes its direction with a sufficient supply of current pulse. [ABSTRACT FROM AUTHOR]

A series of hysteresis loops with off-axial external magnetic fields have been measured to identify magnetization reversal properties as well as coupling effects in magnetic tunnel junctions (MTJs). MTJ films, consisting of a synthetic artificial antiferromagnetic pinned layer of CoFeB/Ru/CoFe/IrMn, were patterned into an elliptical cell array with sizes of 200 × 300 nm and 500 × 750 nm. The hysteresis loops were measured using a vibrating sample magnetometer with various directions of the external magnetic field; the angle θ between the external magnetic field (Hvector E) and the biasing field of the pinned layer (Hvector B) was varied from 0° to 90°. The two significant coupling effects, ascribed to exchange bias between CoFe/IrMn and Ruderman-Kittel-Kasuya-Yosida-like coupling in CoFeB/Ru/CoFe, can be observed in these hysteresis loops. The angular dependence of the hysteresis loops is employed to characterize the variation of these coupling effects in extended and patterned MTJ films. [ABSTRACT FROM AUTHOR]

Abstract: Single crystal neutron diffraction studies have been performed on the rare-earth ternary compound, DyNiSn. This crystal exhibits an incommensurate magnetic structure expressed by the propagation vector, Q =(0.6620.3520) with its third harmonics at low temperatures. In an external magnetic field applied along the c-axis DyNiSn shows incommensurate modulation with Q =(10.3150) at 1.6K, while along the easy magnetization direction of the b-axis a commensurate modulation with Q =(2/300) develops at 2K. The results along the b-axis are fully consistent with the magnetization curve. [Copyright &y& Elsevier]

Abstract: The interlayer coupling field (H in) and coercivity (H c) were measured using micro-optical Kerr effect, and the surface roughness was obtained by using atomic force microscopy (AFM) at different points across the patterned tunnel junction. H in and H c increase with greater surface roughness. This result shows that the enhanced coercivity (H ce) is linearly proportional to H in such as . Finally, the propositional constant α has been deduced from the annealing field dependence of H in and H ce as the function of surface magnetization of pinned layer, . From the results of H in and H ce in magnetic tunnel junction (MTJ) multilayer, we can infer that the surface magnetization of pinned layer is due to the interfacial morphological corrugations. [Copyright &y& Elsevier]

Abstract: We have investigated the angular dependence of exchange bias (H ex) and coercivity (H c) in polycrystalline CoFe (100nm)/MnIr(x) bilayers with x=0, 2, 4, 10 and 20nm. The angular dependence of H ex and H c show the abrupt kinks at critical angle (θ c) in the samples of H c>H ex. The profiles of angular dependent H ex is changed at critical antiferromagnetic layer thickness and shows inverse proportional behavior with field angle from 90°−θ c to 90°+θ c. These complex angular dependence of H ex and H c with antiferromagnetic layer thickness can be well explained by using the Stoner–Wohlfarth (S–W) model. [Copyright &y& Elsevier]