Ferromagnetic materials with high spin polarization are highly suitable materials for the spin transfer torque based magnetoresistive random access memories. In this regard, spin gapless semiconductor (SGS) materials such as quaternary Heusler Alloy CoFeMnSi (CFMS) are very promising candidates for the same because of their unique band structure [1]. However, all these exotic properties are susceptible to the microstructure of the grown film. Therefore, optimized growth of a SGS material is a prerequisite for its practical realization in spintronic-based devices. Here, in this study we have tailored the structural ordering in CFMS thin films (~60 nm) grown at different substrate temperatures (TS) from 150oC to 550oC range over Si(100) substrates using pulsed DC magnetron sputtering. All the grown films were polycrystalline in nature with an enhancement in structural ordering with Tc. Among all the film samples, the film grown at 550oC showed the optimal structure with L21 ordering. The magnetic measurements revealed that saturation magnetization (Ms) of the sample decreased with the measurement temperature with a value ~3.42 μB/f.u. at 5K to 3.11 μB/f.u. at 300 K. The Curie temperature (TC) of the sample was found to be 778±13K. The longitudinal resistivity measurement clearly exhibited a negative temperature coefficient of resistivity, indicating the semiconducting behavior of these CFMS films. The carrier concentration (n) and mobility (μ) were found to be nearly temperature-independent, revealing typical SGS characteristics. The room temperature n and μ values were found to be 3.9 ± 0.04 cm-3 and 88.83 ± 1.58 cm2/V.s, respectively. The temperature-dependent anomalous Hall effect measurements have also been carried out to identify the dominant scattering mechanisms occurring in these films. This measurement suggests the dominance of phonon-induced scattering over impurity-induced scattering.

![](https://assets.underline.io/uploads/markdown_image/1/image/36480f5387b1c5c03309ccafab5e5fa1.jpg)

Fig. 1: (a) GIXRD spectra of the samples grown at different TS, (b) longitudinal resistivity (and/or conductivity at the inset) vs. temperature curve, and (c) Hall resistivity vs. magnetic field recorded at different temperatures (5K to 250K) for A-550 film. Hall resistivity data at 300K is shown in the inset.

Investigation of Spin Gapless Semiconducting Behaviour in Quaternary CoFeMnSi Heusler Alloy Thin Films on Si (100)

**Session chair:** Jorge Puebla, RIKEN



GPC - Fundamental Spintronics II

poster

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This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

Vireshwar Mishra

1

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Investigation of Spin Gapless Semiconducting Behaviour in Quaternary CoFeMnSi Heusler Alloy Thin Films on Si (100)

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