Search

From multicomponent high-entropy alloys (AlCoCrFeNi) through ternary alloys (CrFeNi) to binary (NiCr) alloys, Cr doping plays a critical role in altering the magnetocaloric properties of the resultant alloys. Magnetocaloric effect (MCE) of Ni100−xCrx (x = 5, 10, 15 at.%) nanogranular thin films were investigated by varying Cr concentration, which demonstrate near room-temperature magnetic entropy change (− ΔSM = 0.08 J/kg K) and relative cooling power (RCP = 25 J/kg) at 10 at.% Cr. The MCE properties are well predicted using a phenomenological model based on magnetization as a function of temperature, and they correlate well with experimentally measured magnetic isotherms. [ABSTRACT FROM AUTHOR]

Single phase nano-crystalline zinc ferrite (ZnFe2O4) thin films were deposited on fused quartz substrate using the pulsed laser deposition technique. The films were deposited at different substrate temperatures. The field dependence of magnetization at 10 K shows hysteresis loops for all the samples. Temperature dependence of the field cooled (FC) and zero field cooled (ZFC) magnetization indicated irreversible behavior between the FC and ZFC data, and the irreversibility depends on the measuring magnetic field. The thermo-magnetic irreversibility in the magnetization data is correlated with the magnitude of the applied field and the coercivity (HC) obtained from the M-H loops. [ABSTRACT FROM AUTHOR]

Nano-crystalline magnetic ZnFe2O4 thin films were deposited in oxygen atmosphere at different substrate temperatures (TS) on amorphous quartz substrate by pulsed laser deposition technique. The TS = 350 °C film was also annealed at different temperatures in air. X-ray diffraction patterns confirmed that all the samples were cubic spinel and the average grain size of the films increased with increasing TS and annealing temperatures (TA). Spontaneous magnetization at different temperature was obtained from the $M$ – $H$ loops. The temperature dependence of magnetization data was fit using Bloch’s law. The value of exchange stiffness constant (D) was calculated using the fit values of Bloch’s constant. The obtained D values were found to gradually decrease with the increase of average grain size. [ABSTRACT FROM AUTHOR]

Single phase nano-crystalline zinc ferrite thin films were deposited by RF-magnetron sputtering on quartz substrate at room temperature (RT) in pure Argon environment and annealed (in air) at different temperatures. Temperature dependence of magnetization was studied on these films using both VSM and by observing FMR (in X band). Value of exchange stiffness constant (D) was obtained by fitting Bloch's law to the low temperature magnetization data. The value of D decreased monotonously with the annealing temperature (TA) of the samples. A film annealed at TA=523 K, exhibited the highest magnetization value. The FMR line width of the films decreased with increase in measurement temperature. At RT (~293 K), the lowest value of line width (ΔH) was 15 kA/m and 13 kA/m in parallel and perpendicular configuration respectively for the sample annealed at TA=623 K. [ABSTRACT FROM AUTHOR]

Zinc ferrite films were deposited on fused quartz substrate at different substrate temperatures using a pulsed laser deposition technique. The deposited samples were ex situ annealed at different temperatures up to 650 °C in air for 2 h. It was found that the spontaneous magnetization of the films depends both on the grain size and on the substrate temperatures. The largest values of spontaneous magnetization for our sample were 3000 G at 300 K and 6600 G at 10 K, for the film deposited at substrate temperature of 450 °C. The ferromagnetic resonance linewidths of the films were found to depend both on substrate and annealing temperatures. A relatively low linewidth of 195 Oe was observed in parallel configuration for the film deposited at 250 °C and annealed at 350 °C. [ABSTRACT FROM AUTHOR]

CoFe2O4/ZnFe2O4 bilayers were deposited by the pulsed laser deposition on amorphous fused quartz substrate at substrate temperature of 350^\circC and in oxygen pressure of 0.16 mbar. The films were studied after ex-situ annealing for 2 h in air at various temperatures up to 650^\circC. The magnetic properties of the bilayers were studied at 300 K and at 10 K. Ferromagnetic resonance was carried out at x-band frequencies at room temperature. It was found that as a result of annealing, the diffusion between Co ferrite and Zn ferrite starts around 350^\circC and leads to a large line width system having magnetization, which remains undetected by Ferromagnetic resonance. [ABSTRACT FROM AUTHOR]