Unveiling Structural, Optical and Magnetic Properties of GaMnSb Thin Films

In this study, we investigated the structural, optical, and magnetic properties of GaSbMn thin films fabricated via magnetron sputtering on a glass substrate. To introduce Mn into the GaSb matrix at low concentrations, the substrate temperatures were varied from 200 °C to 400 °C. The X-ray results show that the thin films are polycrystalline with a preferential orientation in the (220) direction of GaSb. accompanied by a secondary phase of MnSb. Raman spectroscopy revealed the presence of vibrational phonon modes of GaSb and a Coupled LO-Phonon-Plasmon Mode (CLOPM). The carrier concentration, derived from , ranged from approximately 1018 to 1019 cm-3. The magnetization behavior was studied using temperature cycling (H fixed) and field cycling measurements (T fixed). The magnetization loops at room temperature show that Mn-doped GaSb films exhibit weak magnetic behavior. The Curie temperature, TC, was determined from the magnetization vs. temperature curves. TC takes high values in the range of 300 K to 570 K, which is related to the formation of MnxSby nanoparticles embedded into the GaSb matrix.

Aims: In this work, we studied the influence of Mn content on GaSb thin films deposited by magnetron R.F. sputtering. To this end, the structural, morphological, optical, and magnetic properties were analyzed and correlated with the experimental conditions.

Study Design: Experimental and theoretical study.

Place and Duration of Study: Laboratorio de Nanoestructuras Semiconductoras, Departamento de Física y Química, Universidad Nacional de Colombia, sede Manizales, Manizales - Colombia, between January 2021 and February 2022.

Methodology: GaSbMn thin films were fabricated using a non-epitaxial growth method, specifically magnetron sputtering, with variations in growth temperature. To study the morphological, structural, optical, and magnetic properties and to correlate these with the experimental conditions, X-ray diffraction, EDS-SEM, Raman spectroscopy, and magnetization measurements were carried out.

Results: GaSbMn thin films exhibit intriguing paramagnetic properties that are contingent upon experimental parameters. Through structural analysis, we identified the formation of MnxSby nanoparticles embedded within the GaSb matrix. The observed MnSb-like phonon modes at 242 cm-1 (LVM), 251 cm-1 (TO), and 264 cm-1 (LO) align well with the reported vibrational modes of MnSb documented in the literature. Estimating a hole density of approximately 1019 cm-3 from the CLOPM frequency in Raman spectroscopy further supports our findings. The Mn2Sb phase predominantly contributes to magnetization at elevated temperatures. Utilizing the mean-field model, we can compute the mean potential resulting from dipolar interactions between any pair of moments
μiand μj at a distance rj

Conclusion: GaAsMn thin films exhibit notable magnetic properties that vary with the growth conditions. Long-range interactions among isolated magnetic moments were analyzed using the mean-field model, demonstrating that the dipolar interaction field is influenced by the growth temperature. The high Curie temperatures observed in the samples are attributed to the presence of the Mn1+xSb phase.