Filmes finos de permalloy crescidos sob campo magnético e temperatura controlados

Abstract

The vertiginous increase in the use of data in today’s society has triggered a frenetic race in the production of media with ever-increasing storage capacity and in new ways of processing information. In this context, spintronics has brought great contributions by proposing a new way of manipulating and processing these data, no longer using the electron charge, but the spin as the information carrier. The study of the growth of thin films and magnetic multilayers and new ways to control their structural and magnetic properties is of great relevance for the development of spintronics and has direct implications for the manufacture of high-density magnetic recording media, which are the most used in large-scale storage.

With that in mind, our group proposes to investigate the effect of simultaneous application of magnetic field and temperature on the growth of thin films. In collaboration with researchers from the National Synchrotron Light Laboratories (LNLS) and Nanotechnology Laboratories (LNNano), located in Campinas - SP, we developed an original experimental arrangement, based on permanent magnets with high working temperature (SmCo), which allows the si-multaneous deposition of 3 films with different field configurations and with temperatures of up to 300∘ on the substrate, using the magnetron sputtering technique. In this work, we investigated how the magnetic field and temperature interfere in the structural and magnetic properties of permalloy-Py films ( 80 20) deposited on substrates of 03 (STO) with orientation ( 001).

For each deposition temperature, samples were produced in three simultaneous magnetic field configurations. The first one with the field in the film plane [along the direction (100) of the STO], another with the field outside the film plane, and a third with no magnetic field (< 30 G, obtained by magnetic shielding with soft iron) . We used 4 different deposition temperatures: 25∘ , 200∘ , 240∘ and 280∘ . In addition, we made two series varying the Py thickness: 10nm and 25nm, totaling 24 samples with different deposition conditions.

We performed structural characterizations using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction and atomic force microscopy. From the EDS we determined the chemical composition of the samples and observed their independence with the magnetic field and the deposition temperature. The other structural characterizations were not conclusive.

The magnetic characterization was carried out using three different experimental tech-niques: the magneto-optical Kerr effect magnetometer (MOKE ), the vibrating sample mag-netometer (VSM) and the ferromagnetic resonance (FMR ). The data obtained allowed us to

observe that all samples presented a predominant anisotropy of shape, that is, the magnetiza-tion is confined to the film plane, but with subtle changes between the different orientations in the film plane, depending on the growth conditions. Comparing the hysteresis of films grown at the same temperature, we observed the appearance of an easy axis along the direction of the deposition field in the plane and a hard axis perpendicular to it, while this behavior is not present in the sample without the deposition field. This behavior is confirmed by FMR measurements.