Structural and magnetic properties of ceramics prepared by high-pressure high-temperature sintering of manganese-doped gallium nitride nanopowders

A precursor system made of Ga(NMe2)3 and Mn[N(SiMe3)2]2 (Me = CH3, initial Mn-contents 5, 10, 20 at.%) upon ammonolysis in refluxing ammonia afforded Ga/Mn amide-imide precursors. The 10 at.% Mn-precursor was nitrided at 500, 700, and 900 °C. The 5 and 20 at.% Mn-precursors were nitrided only at 900 °C. All nanopowders were characterized by XRD, FT-IR, SEM/EDX, whereas some by Raman spectroscopy and XRF. Magnetization measurements were performed with a SQUID magnetometer. Each nanopowder was subjected to no additive high-pressure high-temperature sintering, 7 GPa, 1000 °C, 10 min, affording ceramic pellets. Their structural and magnetic properties were examined to appraise an extent of Mn-incorporation into GaN under sintering conditions. In all samples, the paramagnetic phase of (Ga, Mn)N was accompanied by an antiferromagnetic residue, the latter resulting from oxidation of air sensitive Mn-excess by-products. (Ga, Mn)N in the ceramics showed increased Mn-contents about 1.6 times higher than in the parent nanopowders.