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• Gd-content gradients influence PMA in both "+δ" and "−δ" samples. • "+δ" has lower H C due to closer T comp , suggesting different Gd-content. • Reversal of AHE loop near T comp indicates sublattice dominance shift. • Decrease in H SF suggests weakened exchange interaction near T comp. • Strong ΔR XY at ± 4 kOe and ± 30 kOe for "−δ" indicates enhanced PMA. Ferrimagnetic rare-earth (RE) – transition-metal (TM) alloys are considered small ferromagnets with antiferromagnetic exchange in sublattices, which makes them a preferable choice for future ultrafast memory-related applications. Here, we explore the magnetic properties of two GdFeCo thin films with tailored vertical composition gradients, achieved by gradually varying Gd concentration across the film thickness. The temperature-dependent magnetic behavior of these films is investigated using anomalous Hall effect (AHE) measurements and SQUID magnetometry. Both films exhibit perpendicular magnetic anisotropy with distinct coercivities, indicating variations in their magnetic properties. The films show RE-dominant behavior at 300 K. Moreover, for the positive composition gradient (+δ) film, the compensation temperature is around 350 K, while the film with a negative gradient (−δ) exhibits a compensation temperature above 400 K. Furthermore, the spin-flop behavior and AHE sign reversal provide insights into the sublattice dominance and exchange interactions within the films. The magnitude of ΔR XY (the difference in AHE resistance at different magnetic fields) is shown to be sensitive to the composition gradient, indicating stronger perpendicular magnetic anisotropy for the "−δ" sample. This study demonstrates the potential of composition engineering to tailor the magnetic characteristics of ferrimagnetic materials for specific spintronics applications. [ABSTRACT FROM AUTHOR]

Among various perpendicularly anisotropic magnetic materials, amorphous rare earth-transition metal RE-TM alloys have attracted much interest due to the advantages of tunable magnetic properties and suitable perpendicular magnetic anisotropy (PMA) strength. In this study, the magnetic properties of the Ta/TbFeCo/MgO structure with various Tb-contents are investigated under different annealing conditions like heating rate and annealing temperature. The samples were annealed at heating rate from 10 °C/min to 50 °C/min and holding time was varied from 10 min to 30 min with annealing temperatures ranging from 100 to 150 °C. We found that fast heating rate and low holding temperature help to improve PMA and significantly increase the saturation magnetization and squareness of the TbFeCo films. [ABSTRACT FROM AUTHOR]

• Investigate the temperature-dependent AHE in sandwich structures composed of two RE-TM FIM layers. • Complex AHE phenomena explained by the magnetization reversal of individual layers, Hall sign reversal, and the SF transition in the GdFeCo layer. • A model is developed to provide a simplified explanation of the origin of these complex AHE loops. • The model unravels the complexity in AHE loops near and far from the T comp. • The model fits well with the experimental results. The anomalous Hall effect (AHE) has been a remarkable tool for characterizing the magnetic properties of thin films with perpendicular magnetic anisotropy. In this study, we investigate the temperature-dependent AHE in sandwich structures composed of two ferrimagnetic (FIM) layers with different coercivities, using rare-earth-transition-metal (RE-TM) materials. Complex triple AHE loops are obtained near the compensation temperature of GdFeCo, and these loops are explained by considering the magnetization reversal of the individual layers, Hall sign reversal, and the spin-flop transition in the GdFeCo layer. A model is developed to provide a simplified explanation of the origin of these complex AHE loops. This study elucidates the mechanism behind the unusual temperature-dependent AHE response of the technologically important RE-TM FIM films for spintronics applications. [ABSTRACT FROM AUTHOR]