Antiferromagnetic Ordering in MnF(salen)

TL;DR

This study identifies antiferromagnetic order at 23 K in MnF(salen), a linear-chain system, using various techniques including specific heat, NMR, and susceptibility, revealing complex magnetic behavior and a possible spin-flop transition.

Contribution

First comprehensive investigation of magnetic ordering in MnF(salen) combining heat, NMR, neutron diffraction, and susceptibility data, revealing antiferromagnetic order and spin-flop phenomena.

Findings

Antiferromagnetic order at 23 K confirmed.

Detection of a spin-flop field around 3.8 T.

Neutron diffraction did not resolve magnetic structure.

Abstract

Antiferromagnetic order at $T_{\mathrm{N}} = 23$ K has been identified in Mn(III)F(salen), salen = H$_{14}$C$_{16}$N$_2$O$_2$, an $S = 2$ linear-chain system. Using single crystals, specific heat studies performed in magnetic fields up to 9 T revealed the presence of a field-independent cusp at the same temperature where $^1$H NMR studies conducted at 42 MHz observed dramatic changes in the spin-lattice relaxation time, $T_1$, and in the linewidths. Neutron powder diffraction performed on a randomly-oriented, as-grown, deuterated (12 of 14 H replaced by d) sample of 2.2 g at 10 K and 100 K did not resolve the magnetic ordering, while low-field (less than 0.1 T) magnetic susceptibility studies of single crystals and randomly-arranged microcrystalline samples reveal subtle features associated with the transition. Ensemble these data suggest a magnetic signature previously detected at 3.8 T for temperatures below nominally 500 mK is a spin-flop field of small net moments arising from alternating subsets of three Mn spins along the chains.