Effect of stress on stripe domain onset in sputtered FeAlN and CoFe films

Abstract

Stripe domains caused by perpendicular anisotropy degrade soft magnetic properties of thin films used in recording heads. In this work, the relationship between stress and the susceptibility to stripe domains in soft magnetic thin films is studied theoretically and experimentally. The critical stripe domain onset thickness of a polycrystalline film with cubic unit cell under a planar, isotropic stress is calculated as a function stress and texture for sputtered FeAlN and CoFe films. In good agreement with experimental data, the results show that the stripe domain onset thickness depends on stress and texture. In the sputtered Co65Fe35 film, a residual stress close to zero helps eliminate the possibility of stripe domains, while in the sputtered FeAlN film, the role played by stress depends on texture. For the most frequently seen (110)-textured FeAlN film, large compressive stresses help reduce the possibility of stripe domains for low and moderate N concentrations.

Observation and analysis of mixed domain states in sputtered Co50Fe50 films

“…[26] for predominant (1 1 0)-texture, where K 1 and K 2 are the magnetocrystalline anisotropy constants, and l 1 0 0 and l 1 1 1 are the magnetostriction constants. The calculated stress-thickness phase diagram, separating stripe from in-plane domains for isotropic and (1 1 0)-textured films is plotted in Fig.…”

Magnetic and structural investigation of growth induced magnetic anisotropies in Fe50Co50thin films

“…Indeed, when sputtering deposition is considered, the deposited film may develop an intrinsic stress, that can be compressive due to the atomic peening process [5]. In this case, as the FeCo magnetostrictive constants are positive [10], the presence of an in-plane compressive stress may favour the development of an outof-plane easy axis of magnetization [11].…”

“…When t = 10 nm, σ f ∼ -600 MPa; taking into account the values of FeCo magnetostrictive constants [10] and the fact that the films are polycrystalline [11], this corresponds to an out-of-plane anisotropy constant, K σ , whose value is equal to 6. constant, K s ∼ -13 · 10 5 J/m 3 , we have that |K s | > K σ , so the shape anisotropy overcomes the magnetoelastic contribution and the samples magnetization preferentially lies in the plane of the film. As t increases, the change in curvature increases and eventually the K σ value overcomes the K s one.…”

Target domains in nanometric Permalloy disks with columnar structure

“…The patterned elements thickness is generally of a few tens of nanometers, with lateral size in the 100 to 1000 nm range. This type of films combining easy-plane anisotropy with a slight out-of-plane anisotropy component, tends to exhibit an homogeneous in-plane magnetization at wafer level below a critical thickness tc and a so-called stripe domain structure above tc [11][12][13][14][15][16][17]. The critical thickness normalized by the exchange length was shown to be a function of the film quality 3 factor = , where is the perpendicular anisotropy constant.…”

“…departing from Ni81Fe19 for NiFe alloys) [13][14][15], and/or to the columnar structure of sputtered samples [11,12], especially in samples deposited in poor vacuum in which impurities accumulate within the grain boundaries [11,12]. In some cases, the induced perpendicular has been shown to be non-uniform along the thickness of the film due to grain coarsening and evolution in the film texture [16].…”