Study on the domain structure and tunable spin orientation in L 1 1 -CoPt/NiFe exchange springs with Ta-spacer

In this study, we investigate the domain structure and tunable spin orientation in L11-CoPt(10nm)/NiFe(tNiFe) with insertion of 2-nm thick Ta-spacer and by varying NiFe-layer thickness, tNiFe =1.0, 2.5, 5.5, 7.0, 8.5 and 10nm. The L11-CoPt layer exhibits a strong perpendicular magnetic anisotropy and NiFe holds in-plane magnetic anisotropy and both were separated by the non-magnetic Ta-spacer. Upon increasing tNiFe, the magnetic hysteresis loops become more and more tilted along with moderate decrease in both H c⊥, and SQR⊥ values; while the estimated tilt angle magnetization (θ M) values tend to increase from 0 to 60°. Interestingly, with the insertion of Ta-spacer, significant enhancement in θ M (=45°) is achieved with tNiFe of ∼3nm in the CoPt/NiFe layers - indicating that increase in tNiFe induces tilting of CoPt spins even in the presence of Ta-spacer. Magnetic force microscopy studies on the the L11-CoPt/Ta/NiFe films revealed maze-like domain patterns and their magnetic phase contrasts tend to decrease with dominant topographic features upon increasing tNiFe. The results obtained with the micro-magnetic simulation on the tilt in anisotropy axis are found to be consistent with the experimental values of θ M

Effect of CoSi2 interfacial layer on the magnetic properties of Si vertical bar CoSi2 vertical bar Sm-Co thin films

Magnetic thin films with a layer sequence of Si vertical bar CoSi2 vertical bar Sm-Co were grown by direct sputter deposition at elevated temperatures, through interfacial diffusion between Si (1 0 0) substrate and the overlying Sm-Co layer. HR-TEM analysis revealed the occurrence of CoSi2 -interfacial layer close to the Si-substrate surface, with controllable thicknesses of similar to 20 and 35 nm at deposition temperatures: 450 and 500 degrees C, respectively. XRD studies confirmed the crystallization of Sm2Co17 and SmCo5 magnetic phases accompanied by the other phases such as CoSi2 and SmCoSi2 due to the intermixing of Co and Si-atoms at higher deposition temperatures. The measured coercivity values are found to be increased from 8.7 to 11.6 kOe at higher CoSi2-layer thickness. The angular-dependent hysteresis measurements demonstrated a distinct isotropic and uniaxial magnetic anisotropy characteristics for the Sm-Co films consisting of 35 and 20-nm thick CoSi2 interfacial layers, respectively and the associated magnetization reversal mechanisms are discussed using the Stoner-Wohlfarth model. The temperature coefficients of remanence (alpha) and coercivity (beta) were determined from the temperature-dependent hysteresis curves. The Sm-Co films consisting of 35-nm thick CoSi2-layer exhibited a better thermal stability with 'alpha' and 'beta' values of 0.35 +/- 0.05%/degrees C and -0.13 +/- 0.02%/degrees C, respectively. The results of present study provide splendid opportunities for exploiting the potential of CoSi2 as an under layer, for growing the Sm-Co films towards high-temperature applications

Interfacial layer formation during high-temperature deposition of Sm-Co magnetic thin films on Si (100) substrates

The interfacial layer that has formed during the deposition of ∼240-nm thick Sm-Co films on the bare Si (100) substrate was investigated at different deposition temperatures, Td,Sm-Co: 400, 450 and 500 °C with respect to structural and magnetic properties of Sm-Co films. X-ray diffraction analysis showed the crystallization of both Sm2Co17(R) and SmCo5(H) magnetic phases. Rutherford back scattering studies demonstrated that the surface-diffusion reactions between the Sm-Co layer and Si-surface not only accompanied by the quasi-layered growth of CoSi2-phase; but also led to the formation of SmCoSi2-phase. Cross-sectional transmission electron microscopy analysis revealed uneven boundary with deeply grown CoSi2-layer and Moiré fringes at limited regions of Co/Si interface. Magnetic measurements showed a square hysteresis loop with maximum values of coercivity (11.6 kOe) and remanence ratio (0.99) for the films grown at 500 °C. Magnetic force microscopy images depicted patch-like domains with increasing phase contrast against Td,Sm-Co. In addition, the changes that has occurred in the magnetization reversal processes accompanied by coercivity enhancement due to higher Td,Sm-Co is discussed in the context of domain morphology and first-order reversal curves