Magnetic behavior of Mn3GaN precipitates in ferromagnetic Ga1−xMnxN layers

Ga1−xMnxN layers (where x ≈ 10.4–12.5%) containing Mn3GaN precipitates were grown on (0 0 0 1) sapphire substrates using molecular beam epitaxy, and were shown to exhibit two ferromagnetic phases. These p-type GaMnN films were revealed to have a well defined hysteresis loop up to T ∼ 200 K, which originates from the appreciable number of Mn3GaN precipitates imbedded in the GaN matrix. The precipitated GaMnN samples exhibited a ferromagnetism due to Mn3Ga clusters mixed with Mn3GaN precipitates in the high temperature region (above 200 K). The Mn3GaN precipitates and Mn3Ga clusters were identified by X-ray diffraction and transmission electron microscopy. Mn3GaN precipitates in the samples with a high Mn concentration have a characteristic transition temperature at T ∼ 200 K, which was characterized from field-cooled and zero-field-cooled magnetization curves.