Abstract
We report here on the complex magnetic structure and magnetocapacitance in NiF2, a non-oxide multifunctional system. It undergoes an anti-ferromagnetic transition near 68.5 K, superimposed with canted Ni spin driven weak ferromagnetic ordering, followed by a metastable ferromagnetic phase at or below 10 K. Our density functional calculations account for the complex magnetic structure of NiF2 deduced from the temperature and the field dependent measurements. Near room temperature, NiF2 exhibits a relatively large dielectric response reaching >103 with a low dielectric loss of <0.5 at frequencies >20 Hz. This is attributed to the intrinsic grain contribution in contrast to the grain boundary contribution in most of the known dielectric materials. The response time is 10 μs or more at 280 K. The activation energy for such temperature dependent relaxation is ~500 meV and is the main source for grain contribution. Further, a large negative magneto capacitance >90% is noticed in 1 T magnetic field. We propose that our findings provide a new non-oxide multifunctional NiF2, useful for dielectric applications.
Highlights
The dielectric permittivity (DP), materials have attracted broad attention for the realization of modern electronic devices with miniaturization, integration, high performance offering potential applications for smaller and faster electronics as well as high energy density storage[1,2,3,4]
High dielectric constant and low loss are required for those applications
A large effort is being devoted to the development and characterization of dielectric materials
Summary
The sharp rise in magnetic susceptibility near this AFM transition signifies the presence of weak FM state as well[25] This may be attributed to the canted Ni spin structure in NiF6 octahedra, as explained earlier in structural properties. In addition to the observed AFM transition, superimposed with canted Ni site spin driven weak FM state, NiF2 is showing an additional magnetic ordering on reducing the temperature below ~10 K, where the magnetic moment showed enhancement with lowering temperature. The observed nonlinear magnetization as a function of field substantiates the presence of weak FM ordering in conjunction with long-range AFM ordering of NiF2 This is consistent with the observed sharp rise in magnetization near AFM transition at TN.
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