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Vol. 1 Issue I, August 2013 ISSN: 2321-9653
INTERNATIONAL JOURNAL FOR RESEARCH IN AP PLIED SCIENCE AN D E N G I N E E R I N G T E C H N O L O G Y (I J R A S E T )
Magnetic and dielectric properties of Li– Ni–Cd ferrites Mr. Naveen Sonipat Institute of Engineering & Management
Abstract The magnetic properties of mixed Li0.5 Ni0.75−x/2 Cd x/2 Fe2 O4 (where x = 0, 0.11, 0.32, 0.53, 0.72 and 0.91) ferrites have been reported. The lattice parameter increases linearly with Cd content, which is attributed to ionic size differences of the cations involved. The saturation magnetization increases with increase in cadmium content up to 0.26 and then it decreases with further addition of Cd. The decrease in saturation magnetization (Ms) above Cd = 0.26 is explained on the basis of canted spin model. The a.c. susceptibility measurements show presence of MD particles in the samples. The initial permeability is found to increase monotonically with cadmium content. It is observed that µ i increases gradually with temperature and then it drops to zero near Curie temperature (Tc ). The continuous decrease of Curie temperature (Tc ) with Cd2+ content is attributed to the dilution of A–B interaction. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Ferrites; Li–Ni–Cd ferrites; Magnetic properties
1. Introduction Lithium ferrite is a unique member of a spinel class of ferrimagnets. For more than a decade lithium ferrite materials have been dominating the field of microwave applications because of their rectangular and square hysteresis loop characteristics, high Curie temperature and large saturation magnetization. Lithium ferrites replace garnets and other ferrites in microwave applications because of their low cost and superior performance [1]. The studies of Li-ferrite with different metal ions such as Ni, Mg, Mn, Ti, Zn and Co have been carried out by many workers [2–5]. Lithium–cadmium ferrite system is the most widely studied system because of its use as latched microwave components, sensors, switching devices etc. [6,7]. However, studies on mixed Li–Ni–Cd have not been carried out. In this communication we report on the magnetic properties of mixed Li–Ni–Cd ferrites.
2. Experimental Ferrites samples with the composition Li0.5 Ni0.75−x/2 Cdx/2 Fe2 O4 (where x = 0, 0.11, 0.32, 0.53, 0.72 and 0.91) were prepared by standard ceramic method, using AR grade components oxides. The presintering of the samples was carried out at 600◦ C for 12 h and final sintering at 1000◦ C for 24 h in
air. Pellets (1 cm diameter and 0.3 cm thickness) and toroids (ID = 1 cm, OD = 1.5 cm) pressed at 8 t in.−2 were used in the measurement of magnetization and initial permeability, respectively. X-ray diffraction (XRD) patterns were obtained using Philips PW-1710 diffractometer with Cu K radiation (λ = 1.5418 Å). The magnetization measurements were carried out using a high field hysteresis loop tracer operating at a constant magnetic field of 3 kOe. The low field a.c. susceptibility measurements were carried out using a double coil apparatus operating at 260 Hz in an r.m.s. field of 7 Oe. The initial permeability measurements on toroidal samples were done using LCR-Q meter (Aplab, model-4912) at a fixed frequency of 1 kHz as a function of temperature.
3. Results and discussion The single-phase spinel nature of the samples was confirmed by XRD patterns. The variation of lattice parameter ‘a’ with Cd content is shown in Fig. 1. It can be seen that the lattice parameter increases linearly with cadmium contents obeying Vegard’s law [8]. The Cd 2+ ions have larger ionic radius (0.97 Å) than Fe3+ (0.65 Å), Ni2+ (0.74 Å) and Li1+ (0.71 Å) ions. The Cd2+ ions successively replace Fe3+ ions on A-site. This results in a increase of lattice parameter with
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