Relation between the microstructure and magnetic properties of BaFe12O19 thin films grown on various substrates

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Abstract

Barium ferrite films grown on sapphire and oxidized silicon substrates exhibit a granular structure with cluster-like magnetic domains. On sapphire, high perpendicular anisotropy can be achieved. The films grown on SiO2/Si develop textures with nearly in-plane c-axis, which induce a large in-plane magnetization.

Introduction

An important requirement for high-density magnetic recording is to realize magnetic media with small grains and low magnetic coupling. Barium ferrite is a magnetic oxide that can satisfy such goal. This material has been applied as permanent magnet and exhibits a large magnetocrystalline anisotropy, which supports: (a) Stable magnetization in very small grains; (b) the easy axis of the magnetization can be hold out of plane in thin film. Moreover, the good chemical stability and mechanical hardness make BaFe12O19 an attractive material for longitudinal as well as perpendicular magnetic recording. BaFe12O19 thin films prepared with different techniques such as sputtering [1], [2], [3] and pulsed laser deposition (PLD) [4], [5], [6], [7], [8], have been the subject of intensive research. In this paper, we present a study on BaFe12O19 thin films grown with PLD on two different substrates (sapphire and SiO2/Si).

Section snippets

Microstructure analyses

Pulsed laser deposition technique was used to grow our barium ferrite layers. More details about the sample preparation can be found in Ref. [7]. Two different substrates were used for the growth and consist of single crystal sapphire with (0 0 1) orientation as well as oxidized silicon with 0.5 μm of SiO2 at the top. In this study, the film microstructure was investigated with SEM and XRD analyses. The magnetic properties and the structure of domains were analyzed by VSM, torque and MFM. As we

Magnetic properties and domain structure

Fig. 3(a) shows the in-plane and perpendicular magnetization loops of BaFe12O19 film grown on sapphire. The perpendicular loop exhibits a large coercivity (Hc=200 kA/m) and a remanence close to 0.65. The shearing in the loop is mainly produced by the demagnetizing field, which reduces the remanence. The in-plane magnetization is quasi linear and saturates at 1300 kA/m, which is close to the anisotropy field of single crystal barium ferrite. Such result shows clearly that the easy axis is

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