Torque-detected ESR of a tetrairon(III) single molecule magnet

Torque-Detected Electron Spin Resonance as a Tool to Investigate Magnetic Anisotropy in Molecular Nanomagnets

“…Previous TDESR measurements [20,21,25] relied on capacitive detection of cantilever deflection due to magnetic torque (capacitively-detected (CD-)TDESR). To this end the capacitance between the CuBe cantilever (on which the sample is mounted) and a copper bottom plate is measured (Figure 1a).…”

“…Alternative electron spin resonance (ESR) detection methods include those where the change in magnetization due to magnetic resonance is measured by superconducting interference device (SQUID) or Hall bar sensors [19]. Some of us as well as others have developed the technique of torque-detected electron spin resonance (TDESR) spectroscopy for the investigation of molecular nanomagnets [20][21][22]. This technique relies on the effect of magnetic resonance on magnetic torque τ = MˆB and hence on the deflection of a cantilever on which the sample is mounted.…”

“…The field resolution depends on the field homogeneity, which is 0.1% over one cm radius, corresponding to 10 G in a 1 T field. However, typical samples used here are of mm size, and, in practice, the field resolution is better than 1 G. Thus far, our investigations were limited to a single sample with a large zero-field splitting, namely [Fe 4 (L) 2 (dpm) 6 ] (Fe 4 ) where Hdpm is 2,2,6,6-tetramethyl-3,5-heptanedione (also known as dipivaloylmethane) and H 3 L is (R,S)-2-hydroxymethyl-2-(2-methyl-butoxymethyl)propane-1,3-diol [20,21]. It is now essential to establish the ability of the technique to probe other sources of magnetic anisotropy, as well as to explore alternative detection methods.…”

Cantilever torque magnetometry on coordination compounds: from theory to experiments

“…The agreement between the experimental and calculated position of the resonances is extremely satisfactory. The TDESR experimental set-up was tested in several configurations to demonstrate the solidity of the method [117] and, more recently, on several coordination compounds with SMM properties [118,119] confirming its broad applicability.…”

“…In Fig. 18a we reported the torque signal (more specifically, the torque difference with and without the microwave beam) versus the photons energy recorded by El Hallak et al at T = 20 K and B = 4.5 T on a single crystal of Fe 4 (L) 2 (dpm) 6 (Hdpm = 2,2,6,6-tetra methyl-3,5-heptanedione, H 3 L = (R,S)-2-hydroxymethyl-2-(2-met hyl-butoxymethyl)propane-1,3-diol) [118]. The five peaks clearly visible in the graph, must be attributed to the transitions between the lowest spin states of the ground S = 5 manifold.…”