On the origin of remanence enhancement in exchange-uncoupled CoFe2O4-based composites

Abstract

Finite temperature performance of hard-soft composite nanomagnets and its dependence on geometry structure of composites J. Appl. Phys. 113, 043913 (2013); 10.1063/1.4788703 A feasible approach for preparing remanence enhanced NdFeB based permanent magnetic composites

Mössbauer and Magnetic Properties of Coherently Mixed Magnetite-Cobalt Ferrite Grown by Infrared Pulsed-Laser Deposition

“…At room temperature (RT), a clear magnetic pattern is observed with no singlet or doublet contribution. Similar spectra have been previously reported for CoFe2O4, [16][17][18][19] confirming that cobalt ferrite is magnetically ordered at room temperature. The highest velocity peak, at 7 mm s -1 , shows a clear assymetry that strongly suggests that at least it involves two different components.…”

Magnetic properties of core/shell-structured CoFe2/CoFe2O4 composite nano-powders synthesized via oxidation reaction

“…26 Unfortunately, for the CoFe 2 /CoFe 2 O 4 composite, this experiment is not easy to perform, because the T C of CoFe 2 O 4 is as high as approximately 800 K. On the other hand, CoFe 2 can be oxidized when the temperature is higher than about 600 K. Therefore, to detect the T C of the …”

“…However, smooth single-phase magnetic hysteresis loops of samples 78CFO and 93CFO were observed at 300 K. This result can be understood by considering the variation in magnetic parameters with temperature. Indeed, the inter-phase exchange coupling becomes weaker with increasing temperature, but the change in the anisotropy constant with temperature should also be considered [26]. Therefore, through the magnetic hysteresis loops of samples CF and 93CFO, the ratios of effective magnetic anisotropy constants (K eff ) of CoFe 2 and CoFe 2 O 4 at 300 K to those at 10 K were also calculated using the law of approach to saturation.…”

Separated CoFe2O4/CoFe nanoparticles by the SiO x matrix: revealing the intrinsic origin for the small remanence magnetization

“…But almost all of the results give the following conclusions: (1) When the content of CF increases, the M s value increases rapidly but is accompanied with a large loss of H c . (2) In some previous reports, the exchange coupling between the hard and soft magnets was detected, but unfortunately the M r /M s ratio was not improved and even many reported M r /M s values were less than 0.5 (Quesada et al 2014;Zan et al 2013a, b, c;Li et al 2015), the expected value theoretically for the uniaxial anisotropy crystal (Vargas et al 2005). By carefully checking the results of the morphology characterizations in the previous reports, the following can be observed: (1) First of all, the prepared CFO particles aggregated seriously, and then they exhibited more severe conglomeration after they were reduced in the high-temperature condition.…”