Study of Spin Configuration in Mn Formate Di-Urea by Proton NMR

Abstract

Antiferromagnetic spin arrangement of Mn formate di-urea is studied by proton NMR measurements below T_N (3.78, K). Observed spectra are compared with possible spin arrangements. The antiferromagnetic moments within the layer point to the direction rotating 15 degrees around the c-axis from the middle direction between the [001]- and [100]-directions. The layer including antiferromagnetic moments rotates following to the stacking of four-fold screw axis along the c-axis. The origin of this spin arrangement is discussed.