Gradual development of antiferromagnetic moment in the giant negative thermal expansion material MnCuGeN ( 0.5)

Kodama, Katsuaki   ; Iikubo, Satoshi*; Takenaka, Koshi*; Takigawa, Masashi*; Takagi, Hidenori*; Shamoto, Shinichi  

The anti-perovskite compound MnCuGeN with has a giant negative thermal expansion coefficient due to the magneto-volume effect near room temperature. Competition between the and antiferromagnetic structures around the magnetic ordering temperature could be the driving force for such a phenomenon. In order to examine this possibility, we performed neutron diffraction experiments on MnCuGeN and N nuclear magnetic resonance (NMR) experiments on MnCuGeN. As a reference material, we also investigated MnNiN, whose spin structure is represented by a linear combination of the and antiferromagnetic components. We conclude that in MnCuGeN (), the antiferromagnetic component is nearly absent and the competition between the and antiferromagnetic structures is irelevant to the giant negative thermal expansion coefficient. The antiferromagnetic ordered moment gradually develops with decreasing temperature. This provides a thorough justification for the analysis presented in the previous letter.