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

Abstract

Abstract:The method of choice for in-depth investigation of the magnetic anisotropy in molecular nanomagnets is high-frequency electron spin resonance (HFESR) spectroscopy. It has the benefits of high resolution and facile access to large energy splittings. However, the sensitivity is limited to about 10 7 spins for a reasonable data acquisition time. In contrast, methods based on the measurement of the deflection of a cantilever were shown to enable single spin magnetic resonance sensitivity. In the area of molecular nanomagnets, the technique of torque detected electron spin resonance (TDESR) has been used sporadically. Here, we explore the applicability of that technique by investigating molecular nanomagnets with different types of magnetic anisotropy. We also assess different methods for the detection of the magnetic torque. We find that all types of samples are amenable to these studies, but that sensitivities do not yet rival those of HFESR.

Tailored homo- and hetero- lanthanide porphyrin dimers: a synthetic strategy for integrating multiple spintronic functionalities into a single molecule

“…Homoleptic dimers P2 Tb2 and P2 Dy2 displayed slightly different magnetic properties to their corresponding monomer complexes: P2 Tb2 , U eff = 15(2) K with τ 0 = 3.6 × 10 –5 s; P2 Dy2 , U eff = 7(2) K with a τ 0 = 4.5 × 10 –5 s. The slight differences in the U eff between mono- and bimetallic complexes is most likely a result of the slight change in the second coordination sphere where the TIPS pendent is replaced by an acetylene resulting in a less symmetric second coordination sphere. Changes to the second-coordination sphere can often influence the magnetic properties of lanthanide ions 15. P2 Dy-Tb also showed similar behaviour to the above with U eff = 9(2) K with τ 0 = 2.9 × 10 –5 s confirming slow-magnetic relaxation at low temperatures.…”

Half‐Integer Spin Triangles: Old Dogs, New Tricks

“…The famous" V 15 "c luster K 6 [V IV 15 As 6 O 42 (H 2 O)]•8H 2 Ow as first reported in 1988 [108] and contained fifteen V IV (S = 1/2) ions in al ayered structure, containing 6/3/6 ions in each layer.Its first magnetic studies [109,110] revealed that, from am agnetic perspective, its low-energy spectrumc ould be approximated by the triangle of the central layer,t he two other layers forming evennumbered and strongly antiferromagnetic rings that were silent in an umber of magnetic and spectroscopict echniques. This complex gave rise to al arge number of experimental investigationsw ith av ariety of techniques, such as magnetometry, [111][112][113] magnetic resonance, [110,[114][115][116][117][118][119][120] neutron scattering, [121,122] and heat capacity. [123] Extensive debate concerned whether the ground state degeneracy lifting wasd ue to DMI [124,125] or an isosceles distortion, [122] as till contentious issue.…”

“…[123] Extensive debate concerned whether the ground state degeneracy lifting wasd ue to DMI [124,125] or an isosceles distortion, [122] as till contentious issue. [118] Interestingly,t he multi-technique description of its low-energy magnetic structure made it au seful "calibration standard" for the development of advanced magnetic resonance techniques. [114,118,120] In the above example, the POM "ligand", though magnetic, could fortuitously be neglected for the purposes of specific spectroscopic and magnetic studies.…”

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.…”