•Magnetization relaxation at different probe widths, sensing currents, and Hall geometries.•Current shunting, Joule heating, and current-induced SOT are responsible for coercivity ...response.•Dependence of domain wall propagation on probe widths.•Device behavior at different circumstances is crucial for practical use.
The understanding of the characteristics of a magnetic layer in a different environment is crucial for any spintronics application. Before practical applications, thorough scrutiny of such devices is compulsory. Here we study such a potential Hall device of MgO-capped Hf/GdFeCo bilayer (FeCo-rich) for magnetization relaxation around nucleation fields at different voltage probe line widths and dc sensing currents. The device is characterized by anomalous Hall measurements in transverse and longitudinal Hall geometries for two different probe widths A (5 µm) and B (1 µm). The coercivities of the Hall loops (ρxy-H and Rxx-H) drop with increasing the sense current for both the probes. For probe B, the sharp and large drop in coercivity (ρxy-H loops) at comparatively lower sensing currents is observed, which is attributed to the negligible current shunting and presence of pinning site at B caused by the patterning process. The average domain wall velocities at various sensing currents for probe B are found to be smaller than probe A, from the transverse and longitudinal Hall geometry magnetization relaxation measurements, which agrees with pinning sites and Joule heating effect at probe B. The notch position in the pattern and the longitudinal Hall resistance curve peak shape suggest the domain wall propagation direction from probe B to probe A in the current channel. This study highlights the domain wall propagation at different nucleation fields, sensing currents, and the Hall probe aspect ratios.
We investigate the Hf/GdFeCo bilayer with the MgO cap layer for both rare earth (RE)-rich and transition metal (TM)-rich configurations of the ferrimagnetic sublattice in the presence of the ...perpendicular field. We study the coercivity using the anomalous Hall effect (AHE) technique by multiple measurements on the same sample. In the first set of measurements and at low electric currents, coercivity sharply drops because of the oxygen diffusion at the interface between MgO and GdFeCo when the AHE probe current is applied. During the subsequent measurements on the RE-rich sample, we observe a moderate decrease in coercivity at low currents and the coercivity increases in a high current range. Such nonlinear dependence of coercivity on electric current can be explained by the competing interplay of the spin–orbit torque (SOT) and the Joule heating effects. On the other hand, for the TM-rich case, the SOT effect is observed over a widely applied current range.
•Sintering temperature (Ts) dependent MR and MCE properties of Pr2/3Sr1/3MnO3.•Better grain connectivity results in improved MR and TCR with Ts.•The MR at Tc is 32% at 1T and 58% at 5T magnetic field ...for the optimized sample.•Maximum entropy change (ΔSMmax) is 7.8Jkg−1K−1 upon the field change of 5 Tesla.•Obtained results suggest that it can be a potential magnetic refrigerant material.
Magneto-resistive and magneto-caloric properties of polycrystalline Pr2/3Sr1/3MnO3 have been studied as a function of sintering temperature (Ts) between 1260 and 1450°C. Reitveld refinement of their X-ray diffraction (XRD) patterns confirms their single phase crystalline structure with orthorhombic Pbnm space group. The point of maximum value of temperature coefficient of resistance (TCRmax) and Curie temperature (Tc) decreased slightly with Ts. Magneto-resistance (MR) and magnetic entropy (ΔSM) increased markedly with sintering temperature. This could be attributed to the observed sharpness of both the magnetic and resistive transitions due to better grain connectivity. Optimum results are obtained for the sample with Ts=1400°C. MR at Tc of the same is found to be as large as 32% at 1T and 58% at 5T magnetic fields. The maximum entropy change (ΔSMmax) near its Tc is 2.3Jkg−1K−1 and 7.8Jkg−1K−1 upon 1T and 5T fields change respectively. These characteristics MR (32% 1T, 58% 5T) and reasonable change in magnetic entropy (7.8Jkg−1K−1, 5T) generate possibility that the optimized compound can be used as a potential magnetic refrigerant close to room temperature.
It is commonly known that the coercivity (Hc) of the rare-earth/transition-metal (RE–TM) compound is tuned based on the varying RE content as compared to the TM component. The drawback of this ...approach is that the Hc changes are permanent. In this work, we investigate the coercivity behaviors of the GdFeCo/Hf/MgO heterostructure where the heavy metal Hf layer is inserted in the middle not only to convert charge current into spin current but also to prevent the oxygen diffusion effect. A strong geometry dependence of coercivity detected on Hall bar devices is attributed to the intrinsic properties of GdFeCo and elucidates that the oxidation issue from MgO on GdFeCo is prevented. By selecting a proper Gd content, we demonstrate that the coercivity can be altered flexibly in a wide range Hcmax/Hcmin≈200% via electric current. We develop a simple model to simulate the roles of Joule heating and spin–orbit torques in the novel behaviors of coercivity. It is verified that the excellent magnetic characteristics of GdFeCo are still preserved while manipulating coercivity by the electric current. Our findings broaden the new magnetic behaviors of RE–TM alloys, making them attractive for tunable magnetic anisotropy.
•Temperature dependent anomalous Hall effect (AHE) in GdFeCo.•Magnetic compensation temperature for sheet film ~240 K and device ~118 K.•In sheet film, spin-flopping is witnessed at 0.6 Tesla close ...to compensation temperature.•Triple loops are observed in AHE hysteresis for the device.•The zero-field and 3 Tesla RAHE scan suggests the Hall signal generates solely from the FeCo moment.•Drop in the 3Tesla RAHE near the compensation is explained by considering the low field spin-flopping.
Here we investigate the temperature dependence of anomalous Hall effect in Hf/GdFeCo/MgO sheet film and Hall bar device. The magnetic compensation temperature (Tcomp) for the sheet film and device is found to be ~240 K and ~118 K, respectively. In sheet film, spin-flopping is witnessed at a considerably lower field, 0.6 T, close to Tcomp. The AHE hysteresis loops in the sheet film have a single loop whereas in the Hall bar device, hystereses consist of triple loops are observed just above the Tcomp. Moreover, the temperature-dependent anomalous Hall resistance (RAHE) responds unusually when a perpendicular magnetic field is applied while recording the RAHE. The zero-field RAHE scan suggests the Hall signal generates solely from the FeCo moment. However, the behavior of 3T-field RAHE scan in which the RAHE drops close to zero near the Tcomp seems to be following the net magnetization response of the device, is explained by considering the low field spin-flopping around the compensation temperature. The results presented here give important insight to understand the complex AHE behavior of ferrimagnets for their spintronic applications.
•Magnetization relaxation in Hf/GdFeCo/SiN as a function of current polarity, probe widths, and notch in the device.•In notched Hall bar, the smaller HC for positive current seems due to valve-like ...behavior from notch.•Notch provides smaller delays for nucleation and switching compared to the no-notch Hall bar.•Narrow probe shows the advantage of comparatively faster and less stochastic switching.•Sense current is another important key to controlling the nucleation delay.
The race-track memory concept relies on domain wall propagation through a magnetic track, which has the potential to change the future course of memory-related applications. Therefore, the materials where one can control the propagation of domain walls are crucial. Further, the stochastic nature of magnetization switching has potential applications in neuromorphic computing. Here we study the propagation of magnetic domains and the stochastic magnetization relaxation in the Gd-Fe-Co Hall bar. The magnetic relaxation of Hall bar devices is studied using anomalous Hall resistance measurements. This study highlights the behavior of magnetization relaxation under various parameters viz., at different magnitudes and directions of sensing currents, Hall probe aspect ratios, and the presence of a notch in the Hall bar. This study shows that the stochastic nature and delay in magnetization relaxation can be controlled by the sensing currents and the Hall bar geometry, which is crucial for magnetization switching-based applications.
In the present communication, measurements of transition temperature, thermal conductivity, thermoelectric power and specific heat have been carried out on pristine and co-doped samples of ...Dy0.95Pr0.05Ba2(Cu0.98 M0.02)3O7−δ system M=Fe, Co, Ni and Zn. The electrical resistivity results show that all the samples exhibit metallic behavior. The thermal conductivity results illustrate that for pristine sample of DyBa2Cu3O7−δ, the expected pronounced hump in thermal conductivity is seen below the transition temperature. The hump is suppressed with 5% Pr-doping and this is further suppressed with co-doping. The thermoelectric power measurements show that the pristine sample exhibits hole-like behavior and this continues for doped as well co-doped samples. Pristine sample shows the expected jump in specific heat and with Pr-doping a slope change is observed near the transition temperature.
•All superconducting samples show metallic trend.•Pure and Pr-doped samples show hump in thermal conductivity below their respective transition temperatures.•Thermo-power shows that the majority charge carries are holes.•Expected jump in specific heat is observed for pristine sample.•The jump in specific heat vanishes with co-doping.
We study the effect of inserting Fe and FeCo thin layers between the MgO and the magnetic layer in the TbFeCo-based perpendicular magnetic tunnel junction (pMTJ). Different half and full structure ...MTJ were prepared and thin layers of Fe and FeCo were inserted between the MgO-TbFeCo interface. It is observed that in both the reference and free layer half structures, the coercivity decreases on inserting Fe or FeCo thin layer. In magnetic tunnel junction full structure, the minor and major loop coercivities increase with FeCo insertion. The transmission electron microscope images of magnetic tunnel junctions show the MgO interface becomes smoother with FeCo-insertion. The difference in the half and full structure magnetic properties attribute to the FeCo crystal orientation. Both the Fe and FeCo insertion gives large coercivity to the MTJ free and reference layers and made the MgO-TbFeCo interface smoother. The magnetic annealing of MTJs shows an advantage over the zero-field annealing. The magnetic annealing up to 250 °C improves the squareness of the MTJ’s. This study suggests that the Fe/FeCo thin layer insertion to the TbFeCo-based MTJ will be useful in the fabrication of high performance magnetic random-access memories.
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