In this Tutorial Review, we will focus on the relatively recent approach to obtain SMMs whose magnetic properties arise from a single first row transition metal (TM) ion in a suitable ligand field that creates magnetic anisotropy. 3,4 Another synthetic strategy has been the use of a single ion to develop monometallic SMMs, an approach which first used lanthanide ions. 2 On a synthetic level, it has also led to the study of the one-dimensional analogues of SMMs, known as single-chain magnets (SCMs).
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Often, this has involved looking at the potential of molecular nanomagnets to fulfil applications in areas such as quantum computing or magnetic refrigeration, as well as how to deposit these molecules on surfaces. Since then this field, which has more generally studied molecular nanomagnets, has undergone several developments. Therefore, it can be imagined that “1” in binary coding could be assigned to the magnetisation along the + z direction, and “0” to the magnetisation along the − z direction. Crucially, magnetisation in either direction is retained when the field is removed. At low temperature, by flipping the orientation of the field, this preferential direction can be reversed that is, switched from lying along the z-axis, to lying along the − z-axis. 1 Mn 12ac has a preferential direction for the resultant magnetisation that arises from the precession of the spin in a magnetic field, caused by the anisotropy associated with the metal ions in the complex. The exploration of this possibility for the compound ♲AcOH♴H 2O (Mn 12ac) led to the establishment of a new class of materials called single-molecule magnets (SMMs). Introduction If a single molecule could be used to encode binary information, then vast increases in data storage density could be achieved with respect to traditional media. (4) Design principles based on the 3d ion used, coordination number, and ligand field generated to target and attain SIM behaviour.ġ. It may be possible to hinder the QTM by applying an additional external dc field. (3) Quantum tunnelling of the magnetisation (QTM) may lead to no out-of-phase component of the dynamic magnetic susceptibility being observed. (2) Slow relaxation in single-ion magnets (SIMs) can be observed, and energy barriers measured, using alternating current (ac) susceptibility measurements. Key learning points (1) Slow relaxation of the magnetisation arises from a single 3d ion under an appropriate ligand field.
His current research interests are in the synthesis & characterisation of molecular magnets and magnetic nanoparticles and the application of high pressure science to magnetic systems. Following postdoctoral positions at the University of Edinburgh, with Professor Richard Winpenny and at the University of Bern in Switzerland, with Professor Hans Güdel, he joined the School of Chemistry at the University of Glasgow in 2003, where he is now Reader. Mark Murrie received his PhD from the University of Manchester in 1997 under the supervision of Professor Dave Garner FRS and Professor David Collison. Since November 2013 he is a Post-Doctoral Research Associate in the group of Mark Murrie in the School of Chemistry at the University of Glasgow, studying the effect of pressure on molecular magnetic materials. During his doctoral studies he undertook several placements in the group of Azzedine Bousseksou at the LCC in Toulouse. Under the supervision of Guillem Aromí at the Universitat de Barcelona, he obtained an MSc (2010) and then a PhD (2013) working in the field of spin crossover. Craig graduated with an MSci (Hons.) in Chemistry from the University of Glasgow in 2008. Since the publication of the first 3d-based SIM, which was based on Fe( II), many other contributions have been made to this field, using different first row TM ions, and exploring varied coordination environments for the paramagnetic ions. Here, the synthetic chemist has a significant role to play, both in the design of ligands to enforce propitious splitting of the 3d orbitals and in the judicious choice of TM ion. Because the magnetic properties of these compounds arise from a single ion in a ligand field, they are often referred to as single-ion magnets (SIMs).
In recent years, there has been a growing focus on maximising the anisotropy generated for a single 3d transition metal (TM) ion, by an appropriate ligand field, as a means of achieving higher barriers. This physical quantity depends on the magnitude of the magnetic anisotropy of a complex and the size of its spin ground state. One of the determining factors in whether single-molecule magnets (SMMs) may be used as the smallest component of data storage, is the size of the barrier to reversal of the magnetisation, U eff.
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