Antiferromagnetic resonance in quasi-one-dimensional ferromagnet γ-p-NPNN

The low frequency (∼300 MHz) and low-temperature (0.4 K) ESR were performed in the γ-phase of p-NPNN, which is considered to be as a quasi-one-dimensional ferromagnet above the antiferromagnetic ordering temperature (0.65 K without a static magnetic field). Below 0.6 K, we succeeded in observing the antiferromagnetic resonance (AFMR) for the first time. The frequency–field relation is well reproduced by the two-sublattice model with orthorhombic anisotropy. In addition, we measured magnetic torque using small single crystal, which has the dimension of 0.25 × 0.10 × 0.10 mm3. A spin–flop transition and AF-paramagnetic (AF-P) transition are observed at 470 and 2100 G at 0.4 K, respectively. Both AFMR and magnetic torque measurements indicate that the spin-easy axis is almost parallel to the direction to phenyl ring from the ONCNO fragments.

Graphical abstractAntiferromagnetic resonance and magnetic torque measurements using piezo-resistive cantilever were performed in the ordered state of γ-phase of para-Nitrophenyl Nitronyl Nitroxide below 0.6 K. A spin-flop transition and AF-paramagnetic transition are observed around 470 Gauss and 2100 Gauss at 0.4 K, respectively. The spin-easy axis is almost parallel to the direction to phenyl ring from the ONCNO fragments.Figure optionsDownload full-size imageDownload as PowerPoint slide