NMR Study on CoCr₂O₄

Abstract

Co⁵⁹ and Cr⁵³ nuclear magnetic resonances (NMR) in the ordered phase of CoCr₂O₄ are studied. At low temperature magnetic phase, two NMR signals are observed. From the magnetic field dependences of these resonance frequencies, up to 50 kOe, the half cone angles of the ferrimagnetic spiral of this material are determined as
φ_Co=18°±7° and φ_Cr=123°±4°.
It is shown that these values are consistent with LKDM theory, if the exchange interactions between distant neighbor ions are taken into account. At high temperature magnetic phase, only Co⁵⁹ NMR is observed, where local moment on Co²⁺ ion seems parallel to the resultant moment.