Negative Thermal Expansion and Correlated Magnetic and Electrical Properties of Si‐Doped Mn ₃ GaN Compounds

The negative thermal expansion (NTE) and correlated magnetic and electrical transport properties of Mn 3 Ga x Si 1− x N were investigated. For pure Mn 3 GaN, there is a large NTE effect corresponding to the antiferromagnetic to paramagnetic transition. Very interestingly, when partial Ga was replaced by Si, the NTE properties around the magnetic transition were changed. The NTE temperature range was broadened to Δ T =148 K for Mn 3 Ga 0.75 Si 0.25 N and the linear thermal expansion coefficient was estimated as β=−1.4 × 10 −5 K −1 (272–420 K). Accordingly, the resistivity also showed a decrease from 327 to 395 K with temperature. With a further increasing Si content to x =0.5, the magnetic transition still occured, but the NTE effect did not appear. After careful observation, an anomaly was found at around 350 K in a – T , ρ– T , and DSC curves of Mn 3 Ga 0.5 Si 0.5 N, respectively. This phenomenon strongly implies the close correlation among lattice, spin, and charge in this series materials.