Magnetic Response of Mn(III)F(salen) at Low Temperatures

Abstract

The low temperature magnetic response of Mn(III)F(salen), salen = H14C16N2O2, an S = 2 linear-chain system, has been studied. Using a single crystal with the eld applied perpendicular to the chain direction, torque magnetometry, down to 20 mK and up to 18 T, revealed a feature at 3.8 T when T ≤ 400 mK. ESR (≈ 200 GHz) studies, using single crystals at 4 K and in 5 T, have not detected any signal. In 10 mT, the temperature dependence of the susceptibility of powder-like samples can be reasonably t when J/kB = 50 K and g = 2. In addition, these data are unchanged for P ≤ 1.0 GPa. Using a randomly-oriented, powder-like, deuterated (12 of 14 H replaced by D) sample of 2.2 g at 270 mK, neutron scattering data, acquired with the Cold Neutron Chopper Spectrometer at the Spallation Neutron Source, show several well dened excitations that may be from the zero-eld energy levels of antiferromagnetic S = 2 spins with g = 2, J/kB = 50 K, D/kB = 2.8 K, and E/kB = 0.5 K.

Antiferromagnetic ordering in MnF(salen)

“…In addition, a net moment for every subset of three Mn atoms is antiferromagnetically arranged along the chains. The torque magnetometry studies reported by Park et al 29 indicate a critical field of 3.8 T for T 500 mK, and this feature is the spin-flop field of the net moment of each subset of three Mn. phonon contribution, so an accurate estimate of the total magnetic entropy removed below the ordering temperature is not possible.…”

“…29 During the course of this work, specific heat and 1 H NMR investigations were initiated, and both experiments provided unambiguous evidence of long-range antiferromagnetic order at T N = 23 K. The purpose of this paper is to present these data sets and the corresponding analyses, which, when combined with neutron powder diffraction at 10 K and 100 K and additional systematic studies of the low-field magnetic response, provide insight into the nature of the magnetic transition.…”

“…Previously, several batches, including the deuterated one, of as-grown, randomly arranged microcrystals provided a response similar to the data reported by Birk et al 28 Specifically, when using the Padé approximations of quantum Monte Carlo simulations, 38 the low-field magnetic susceptibility at high temperatures was well fit when J = 50 ± 2 K for g = 2. 29 After the discovery of the specific heat and NMR signatures of long-range antiferromagnetic ordering at T N = 23 K, the magnetic susceptiblity studies were extended to include a single crystal and zero-field-cooling (ZFC) versus field-cooling (FC) study of a fresh (less than one-month old) as-grown microcrystalline sample. The results shown in Fig.…”

“…[20][21][22][23][24][25][26][27] Recently, a new S = 2 linear-chain system, MnF(salen), salen = H 14 C 16 N 2 O 2 , was synthesized, and the low-field, high-temperature magnetic properties were fit with J/k B ≈ 46 K, while no evidence of a magnetic transition was detected down to 1.8 K. 28 This report motivated a suite of studies, including torque magnetometry and EPR on single crystals and neutron scattering on a partially deuterated, as-grown, microcystalline powderlike sample, and a brief report of the resulting data sets are published elsewhere. 29 During the course of this work, specific heat and 1 H NMR investigations were initiated, and both experiments provided unambiguous evidence of long-range antiferromagnetic order at T N = 23 K. The purpose of this paper is to present these data sets and the corresponding analyses, which, when combined with neutron powder diffraction at 10 K and 100 K and additional systematic studies of the low-field magnetic response, provide insight into the nature of the magnetic transition.…”

“…exchange via fluoride ion bridges [29] have been reported. The initial report by Birk et al [28] motivated a suite of studies, including torque magnetometry and EPR on single crystals and neutron scattering on a partially deuterated, asgrown, microcystalline powderlike sample, and a brief report of the resulting data sets has been published elsewhere [30]. During the course of this work [30], specific heat and 1 H NMR invest igations were initiated, and both experiments provided unam biguous evidence of longrange antiferromagnetic order at = T 23 N K. The purpose of this paper is to present these data sets and the corresponding analyzes, which, when combined with additional studies of the lowfield magnetic response, provide insight into the nature of the magnetic transition.…”