Exchange bias training effect in NiFe₂O₄/NiO nanocomposites

Abstract

Exchange bias field (HEB) accompanying vertical magnetization shift (ΔM) is observed in a granular system composed of ferrimagnetic (Ferri) NiFe2O4 nanoparticles embedded in an antiferromagnetic NiO matrix, after the sample is cooled from 350 to 10 K under a 40 kOe magnetic field. Consecutive hysteresis loops show that both HEB and ΔM decrease with magnetic field cycling, which is referred to as the training effect. Furthermore, HEB shows a linear dependence on ΔM throughout the training procedure, and HEB originates mainly from the cycle-dependent shift of the left coercivity (HC1) while the right coercivity (HC2) remains almost constant. This observed training effect is interpreted in the framework of the spin configurational relaxation model.

Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys

“…4(b) were fitted using the Equation (2), giving H E ∞  = 1210 Oe. This training effect was interpreted in terms of metastable magnetic disorder at the magnetically frustrated interface during the magnetization reversal process for SEB2122.…”

Exchange bias and training effect in Ni/Ag-doped NiO bilayers

“…8(b)). The abrupt single cycle training between n=1 and 2 is also found in other systems, such as Co/CoO, Co/FeMn and NiFe 2 O 4 /NiO systems [29][30][31]. To include the steep reduction for n=1, Binek and coworkers [32,33] considered the training effect in the AF/F system in the framework of nonequilibrium thermodynamics.…”

Switching on Antiferromagnetic Coupled Superparamagnetism by Annealing Ferromagnetic Mn/CdS Nanoparticles

“…The amount of exchange bias can be calculated from the equation of H EB = À(H C1 þ H C2 )/2, where H C1 and H C2 are respectively of right and left coercive fields of the hysteresis loop. 35 From this equation, the measured H EB values for both 20 and 8 K are 71 and 150 Oe, respectively. This again confirms the interparticle interaction in the system leading to subtle shifts from the center of the M vs H curve.…”