High-Temperature Thermal Cycling Effect on the Irreversible Responses of Lattice Structure, Magnetic Properties, and Electrical Conductivity in Co_2.75Fe_0.25O_4+δ Spinel Oxide

Abstract

We report high temperature synchrotron Xray diffraction (SXRD), dc magnetization and currentvoltage (IV) characteristics for the samples of Co 2.75 Fe 0.25 O 4 ferrite. The material was prepared by chemical reaction of the Fe and Co nitrate solutions at pH  11 and subsequent annealing at temperatures 200 0 C, 500 0 C and 900 0 C. The measurements were performed by cycling the temperature from 300 K to high temperature (warming mode) and return back to 300 K (cooling mode). The SXRD patterns indicated a fine biphased cubic spinel structure in the highly Co rich spinel oxide. Magnetization curves showed intrinsic ferrimagnetic features and defect induced additional ferromagnetic phase at higher temperatures. Electrical conductivity showed thermal hysteresis loop between warming and cooling modes of temperature variation.The samples exhibited new information on the irreversibility phenomena of lattice structure, magnetization and electrical conductivity on cycling the measurement temperatures.

Probing low temperature non-equilibrium magnetic state in Co2.75Fe0.25O4+δ spinel oxide using dc magnetization, ac susceptibility and neutron diffraction experiments

“…Synchrotron X-ray diffraction sites. The range (0.260-0.263) of u values in the samples is consistent to the reported values [17].…”

“…In CF50 sample, the low temperature peak (T m1 = 47 K for MZFC and 30 K for MFC) is more prominent than that in high temperature peak (T m2 = 205 K for MZFC and 175 K for MFC). One more high temperature peak seems to exist above 330 K for the CF50 sample and it was noted at 375 K from high temperature measurements [17]. The reduction of peak temperatures in the MFC(T) curve in comparison to the MZFC(T) curve at shows magnetic field induced spin order in the samples and it is expected due to anisotropy effect of small particles.…”

“…4(c-d 1. The calculated parameters may not be true values as the system is not completely free from magnetic exchange interactions in the temperature range that is well below of the real paramagnetic state (> 300 K) [17]. However, it can provide useful information for the nature of local magnetic spin order in the low temperature and high temperature regimes.…”

“…The long ranged magnetic spin order is perturbed under the site exchange of Co and Fe ions and lattice disorder in A and B sites [2,12]. The non-equilibrium spinel structure, e.g., spinodal decomposition (Co-rich and Fe-rich phases), and its impact on tuning the magnetic and electronic properties have emerged as promising research fields [11][12][13][14][15][16][17]. Such materials with inhomogeneous lattice structure and magnetic spin order are interesting for basic understanding of the first order magnetic phase transition, and achieving high magneto-caloric effect and high performance catalytic activities in spinel oxides [12,[18][19][20].…”

“…Despite of showing many unusual magnetic properties in Co rich spinel oxides, there is not much progress on studying their non-equilibrium magnetic properties. We reported the nonequilibrium ferrimagnetic properties of Co 2.75 Fe 0.25 O 4 spinel oxide at lower temperatures in the range 10-340 K (preliminary information for one sample that was heated at 500 0 C [21]) and at higher temperatures (300-950 K) for the samples that were heated at different temperatures [17].…”