Beating Thermal Deterioration of Magnetization with Mn(4)C and Exchange Bias in Mn–C Nanoparticles

The magnetization of most materials decreases with increasing temperature due to thermal deterioration of magnetic ordering. Here, we show that Mn(4)C phase can compensate the magnetization loss due to thermal agitation. The Mn–C nanoparticles containing ferrimagnetic Mn(4)C and other Mn–C/Mn-O phases were prepared by using the traditional arc-discharge method. A positive temperature coefficient of magnetization (~0.0026 Am(2) kg(−1) K(−1)) and an exchange bias up to 0.05 T were observed in the samples. We ascribe the exchange bias to the co-existence of ferrimagnetic Mn(4)C/Mn(3)O(4) and antiferromagnetic α-Mn(C)/MnO phases. The positive temperature coefficient of magnetization of the samples was ascribed to the presence of Mn(4)C phase, which is considered as a Néel’s P-type ferrimagnet.