Negative magnetization and the sign reversal of exchange bias field in Co(Cr1-xMnx)2O4 (0≤x≤0.6)

Abstract

A series of Co(Cr1-xMnx)2O4 (0 ≤ x ≤ 0.6) ceramic samples have been synthesized by using the sol-gel method. The magnetic properties of the ceramics are experimentally studied through different protocols of dc magnetization measurements. It is found that Mn-doping continuously decreases the total magnetization for x in the range of 0 ≤ x ≤ 0.2 and the net magnetization becomes negative in the range of 0.3 ≤ x ≤ 0.5. The net magnetization reverses and becomes positive upon further increasing x to 0.6. This unusual magnetic phenomenon in the system for x = 0.3–0.5 can be called as negative magnetization. It is regarded as arising from the competition of the two magnetic sublattices at different crystallographic sites. For the sample x = 0.3, the magnetic switching effect near the compensation temperature Tcomp has been studied, and it shows potential applications in the spintronic devices. The magnetic configuration of the sample could be changed under a high magnetic field, and the spin is reoriented at TSR. Both positive and negative exchange bias effects are observed, which are ascribed to the pinning force of uncompensated spins on ferromagnetic moments and the magneto-structural transition, respectively.

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr1.7Fe0.3O4 Nanoparticles

“…Below T C , the irreversibility between the M FC and M ZFC is observed at irreversible temperature, T irr ≈ 244 K. The large bifurcation between the M FC and M ZFC below T irr suggests the presence of uncompensated spins accompanied by strong magnetic anisotropy. [ 19 ] The spin‐spiral ordering temperature, T S , which has been reported at around ≈28–31 K in NiCr 2 O 4 , could not be observed in the present sample. The absence of T S suggests a further decrease in B–B exchange interaction at the cost of increase in A–B exchange interaction.…”

Neutron diffraction evidence for local spin canting, weak Jahn–Teller distortion, and magnetic compensation in Ti1−x Mn x Co2O4 spinel

“…Such dilution (with tetravalent nonmagnetic elements like Sn 4+ , Ge 4+ or Ti 4+ ) play a major role in the disruption of antiferromagnetic ordering in Co 3 O 4 and results in a short-range ordering with reentrant spin-glass (RSG) behavior [19,20,27,28]. Coexistence of ferrimagnetic behaviour with RSG, negative magnetization below the compensation temperature and giant asymmetry in the hysteresis loops are some of the important features noticed in such diluted inverse spinels [19,20,[27][28][29]. Nevertheless, diluting the octahedrally coordinated Co 3+ ions with magnetic element Mn 3+ leads to the formation of inverse spinel MnCo 2 O 4 which has tremendous applications in the renewable energy sector, such as, solid-oxide fuel cells, lithium-ion batteries, catalysis and magnetoelectronics [30][31][32].…”

Negative magnetization and magnetic ordering of rare earth and transition metal sublattices in NdFe0.5Cr0.5O3

“…Thereafter, with further increase in temperature the magnetization remains negative in the temperature range of 25.5 K < T < 150.5 K and it becomes positive at around 150.5 K. The temperature range of 25.5 K < T < 150.5 K where magnetization remains negative is much larger than that of NdFeO 3 , one of the parent compounds which also shows negative magnetization in ZFC mode [31]. Negative magnetization in ZFC mode is quite a rare incident and there are few reports available in the literature [31][32][33][34][35]. Although, uncompensated spins [31,32], trapped field in magnetometer [33] or disorder [34] etc.…”

“…Negative magnetization in ZFC mode is quite a rare incident and there are few reports available in the literature [31][32][33][34][35]. Although, uncompensated spins [31,32], trapped field in magnetometer [33] or disorder [34] etc. are considered to be the reasons for MR, still there are doubt about the origin of it.…”