Studies on Magnetic, Transport and Dielectric Properties of Ni0.65Zn0.35Fe2O4 Thin Films Grown by Pulsed Laser Deposition

The ferrimagnetic material Ni_1-xZn_xFe₂O₄ (NZFO) has drawn tremendous attention in recent years due to its potential applications in radio frequency coils, transformer cores, rod antennas, magnetic cores of read write heads for high-speed digital tape or disk recording and microwave devices owing to its remarkable magnetic properties, high resistivity and low eddy current. Other than these the NZFO is also considered as potential candidate for multiferroic composite structures.  We have chosen Ni_0.65Zn_0.35Fe₂O₄ for the present investigation as this composition exhibits the highest saturation magnetization in the entire Ni–Zn family along with high magnetic curie temperature which is ~ 575 K. NZFO thin films were grown by pulsed laser deposition (PLD)  at different substrate temperatures in the range of 500-800^oC using a KrF excimer laser (λ=248 nm) on LaNiO₃ buffered (001) oriented (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 substrates under oxygen pressure of 150 mTorr. These films were subsequently annealed at their respective growth temperature for 30 min in oxygen ambient at a partial pressure of ~ 300 Torr. The highly c-axis oriented growth containing only (004) diffraction peak of NZFO films along with in-plane epitaxial relationship was confirmed by high resolution X-ray diffraction measurements. From the atomic force micrographs it was observed that all the films were densely packed, smooth, free from microcrack and particulates with uniform grain-size distributions. X-ray Photoelectron Spectroscopy measurements confirmed that in all films the Ni, Zn and Fe elements retain their same oxidation states as in bulk target irrespective of growth temperature. The saturation magnetization (M_s) of NZFO film was found to enhance systematically with increasing growth temperature. The resistance of NZFO films was found to decrease with increasing temperature indicating insulating behaviour. These films showed positive magneto resistance at low magnetic fields. Detailed dielectric, magnetic, magneto resistance and transport characterizations are currently underway and results will be discussed at the meeting.