Spin dynamics in single-molecule magnets combining surface acoustic waves and high-frequency electron paramagnetic resonance

Maciá, Ferran; Lawrence, J. M.; Hill, Stephen; Hernández, J. M.; Tejada, J.; Santos, P. V.; Lampropoulos, Christos; Christou, George

doi:10.1103/physrevb.77.020403

Cited by 13 publications

(4 citation statements)

References 16 publications

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“…On the other hand, EPR and HFEPR (see for example ref. [213][214][215][216][217][218][219] have been extensively used to characterize the anisotropy parameters of all kinds of SMM and molecular magnetic materials. Still, the small quantity of material available in the case of thin films of magnetic molecules or nanostructured molecular materials on surfaces makes it almost impossible to apply these conventional bulk techniques for its magnetic characterization, and further developments are needed.…”

Section: Magnetic Resonance Techniquesmentioning

confidence: 99%

“…Some interesting variations of these techniques that could be envisaged for further experiments on SMMs on surfaces include the detection of EPR via magnetization measurements with a Hall probe magnetometer, 220 detection of the magnetization transitions in a sample by microwave absorption experiments in a resonant cavity, 221 or combination of surface acoustic waves with HFEPR measurements. 218 A few examples of EPR measurements on SAM are available in the literature. Veciana and co-workers measured the EPR spectrum at room temperature of bistable organic PTM radical derivatives (bearing a thioacetate and a disulfide group) in the form of SAM on a surface area of 66 mm 2 and contrasted it with a spectrum of the same SAM of a PTM anion.…”

Section: Magnetic Resonance Techniquesmentioning

confidence: 99%

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Advances on structuring, integration and magnetic characterization of molecular nanomagnets on surfaces and devices

2012

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This critical review represents a concise revision of the different experimental approaches so far followed for the structuration of molecular nanomagnets on surfaces, since the first reports on the field more than ten years ago. Afterwards, a presentation of the different experimental approaches followed for their integration in sensors is described. Such work involves mainly two families of sensors and devices, microSQUIDs sensors and three-terminal devices for single-molecule detection. Finally the last section is devoted to a detailed revision of the different experimental techniques that can be used for the magnetic characterization of these systems on surfaces, ranging from magnetic circular dichroism to magnetic force microscopy. The use of these techniques to characterize other nanostructured magnetic materials, such as nanoparticles, is also revised. The aim is to give a broad overview of the last advances achieved with these techniques and their potential and evolution over the next years.

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Section: Magnetic Resonance Techniquesmentioning

confidence: 99%

Section: Magnetic Resonance Techniquesmentioning

confidence: 99%

Advances on structuring, integration and magnetic characterization of molecular nanomagnets on surfaces and devices

2012

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“…Consequently, these two molecules have contributed to many of the most important discoveries associated with the magnetization dynamics of isolated SMMs, i.e. QTM, magnetic quantum phase interference (QPI) [31], magnetic avalanches [32,33], etc. Moreover, Mn 12 and Fe 8 are readily available (and easily synthesized) as good sized single-crystals with well defined shape/morphology, simplifying identification of the principal magnetic axes and, hence, alignment for magnetic studies.…”

Section: Introductionmentioning

confidence: 99%

Magnetic quantum tunneling: insights from simple molecule-based magnets

et al. 2010

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This perspectives article takes a broad view of the current understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 II 4 Ni , III 3 Mn (S = 2 and 6) and III 6 Mn (S = 4 and 12). The Mn III complexes are related by the fact that they contain triangular III 3 Mn units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn III centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low-and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Comparisons are made between the giant spin and multi-spin phenomenologies. The giant spin approach assumes the ground state spin, S, to be exact, enabling implementation of simple anisotropy projection techniques. This methodology provides a basic understanding of the concept of anisotropy dilution whereby the cluster anisotropy decreases as the total spin increases, resulting in a barrier that depends weakly on S. This partly explains why the record barrier for a SMM (86 K for Mn 6 ) has barely increased in the 15 years since the first studies of Mn 12 -acetate, and why the tiny Mn 3 molecule can have a barrier approaching 60% of this record. Ultimately, the giant spin approach fails to capture all of the key physics, although it works remarkably well for the purely ferromagnetic cases. Nevertheless, diagonalization of the multi-spin Hamiltonian matrix is necessary in order to fully capture the interplay between exchange and local anisotropy, and the resultant spin-state mixing which ultimately gives rise to the tunneling matrix elements in the high symmetry SMMs (ferromagnetic Mn 3 and Ni 4 ). The simplicity (low-nuclearity, high-symmetry, weak disorder, etc..) of the molecules highlighted in this study proves to be of crucial importance. Not only that, these simple molecules may be considered among the best SMMs: Mn 6 possesses the record anisotropy barrier, and Mn 3 is the first SMM to exhibit quantum tunneling selection rules that reflect the intrinsic symmetry of the molecule.

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“…15 In turn, these avalanche phenomena have themselves become the focus of much recent attention in Mn 12 -acetate. 16,[47][48][49][50] More dramatically, it has been shown by Morello et al, 51,52 that the coupled nuclear spin-lattice dynamics is strongly influenced by the FR species in the low-temperature regime where the SR molecules are completely blocked and, thus, should not mediate any coupling between the nuclear spins and the lattice. Therefore, these findings motivated more detailed spectroscopic investigations, as described in this article.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy barrier reduction in fast-relaxingMn12single-molecule magnets

2009

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A novel angle-swept high-frequency electron paramagnetic resonance (HFEPR) technique is described that facilitates efficient in-situ alignment of single-crystal samples containing lowsymmetry magnetic species such as single-molecule magnets (SMMs). This cavity-based technique involves recording HFEPR spectra at fixed frequency and field, while sweeping the applied field orientation. The method is applied to the study of a low-symmetry Jahn-Teller variant of the extensively studied spin S = 10 Mn 12 SMMs (e.g. Mn 12 -acetate). The lowsymmetry complex also exhibits SMM behavior, but with a significantly reduced effective

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Spin dynamics in single-molecule magnets combining surface acoustic waves and high-frequency electron paramagnetic resonance

Cited by 13 publications

References 16 publications

Advances on structuring, integration and magnetic characterization of molecular nanomagnets on surfaces and devices

Advances on structuring, integration and magnetic characterization of molecular nanomagnets on surfaces and devices

Magnetic quantum tunneling: insights from simple molecule-based magnets

Anisotropy barrier reduction in fast-relaxingMn12single-molecule magnets

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