Presence of mixed magnetic phase in mechanically milled nanosized Co0.5Zn0.5Fe2O4: A study on structural, magnetic and hyperfine properties

In this paper, we have presented a detailed study on the effects of mechanical activation caused by high energy ball milling on the structural, magnetic and hyperfine properties of nanosized Co0.5Zn0.5Fe2O4 having three different particle sizes 63 (M1), 25 (M2) and 17 nm (M3) synthesized by chemical coprecipitation method. Characterization techniques like powder x-ray diffraction, high resolution transmission electron microscopy, dc magnetic measurements and Mossbauer spectroscopic techniques have been employed to examine M1, M2 and M3 thoroughly. All the three samples are cubic spinel ferrites with Fd (3) over barm symmetry. The lattice parameters of M1, M2 and M3 are 8.395, 8.391 and 8.375 angstrom, respectively. The particles constituting all the three samples possess both superparamagnetic and ferrimagnetic phases at room temperature. The values of blocking temperature of M1, M2 and M3 are 204, 210 and 220 K, respectively. The values of saturation magnetization of M1, M2 and M3 at 300 and 10 K are 56.8, 55.3, 51.5 emu g(-1) and 115.68, 113.84, 109.65 emu g(-1), respectively. The values of coercivity for M1, M2 and M3 at 10 K are 1395, 2190 and 1950 Oe, respectively. The theory of magnetic domains has been exploited to explicate the trend in coercivity. The cation distribution of M2 is (Zn0.482+Fe0.523+)(A)[(Co0.5+Zn0.02+Fe1.483+)-Zn-2-Fe-2](B)O-4. The effects of mechanical activation on cation redistribution and magnetic property of M2 have been investigated by infield Mossbauer spectroscopic measurements and verified by theoretical analysis of experimental results of Rietveld refinement of powder x-ray diffraction data in conjugation with dc magnetic study. The sample M2 is basically ferrimagnetic in nature possessing a slightly canted core surrounded by a disordered shell. It exhibits excellent memory effect in its dc magnetization measurement. The sample is capable of encoding, preserving and recalling binary numbers through magnetic field change. This property of the sample may be used to design magnetic coding and sensing devices.