Tuning the bimetallic amide-imide precursor system to make paramagnetic GaMnN nanopowders

• New bimetallic precursor system for conversion to GaN/Mn nanopowders was designed.
• Two conversion routes were applied with precursor nitridation at 500, 700 or 900 °C.
• Prepared nanopowders were thoroughly characterized including magnetic measurements.
• The major product was the gallium nitride Mn-doped phase GaMnN with 2–3 at.% of Mn.

A bimetallic molecular system made of gallium (III) tris(dimethyl)amide Ga(NMe2)3 and manganese (II) bis(trimethylsilyl)amide Mn[N(SiMe3)2]2 (Me = CH3, fixed initial Mn-content 10 at.%) was subjected to ammonolysis in refluxing/liquid ammonia. Upon isolation at room temperature, the amide-imide mixed metal precursor was pyrolyzed at elevated temperatures under an ammonia flow by two different routes. Route 1 consisted of a direct nitridation at high temperatures of 500, 700 or 900 °C. In route 2, a low temperature pyrolysis at 150 °C was applied prior to nitridation at the same final temperatures as in route 1. All nanopowders were characterized by XRD diffraction, FT-IR spectroscopy, and SEM/EDX microscopy and analysis. Thorough magnetization measurements in function of magnetic field and temperature were carried out with a SQUID magnetometer. In all samples, the paramagnetic phase of GaMnN was accompanied by an antiferromagnetic by-product linked to a Mn-containing species from decomposition and oxidation of Mn-precursor excess. The Mn-contents in the crystalline GaMnN, i.e., Mn-incorporated in GaN crystal lattice, were of the order of 2–3 at.% mostly independent on the nitridation route whereas the latter had a pronounced effect on amounts of the antiferromagnetic by-product.