Keywords: single-molecule magnets, molecular nanomagnets, molecular spintronics, magnetic hysteresis, resonant quantum tunnelling, quantum interference, spin parity effect, decoherence, quantum computation, qubit, exchange-bias, spin-Hamiltonian, micro-SQUID, magnetometers, nanotechnology
Molecular nanomagnets: towards molecular spintronics
Molecular nanomagnets, often called single-molecule magnets, have attracted much interest in recent years both from experimental and theoretical point of view. These systems are organometallic clusters characterised by a large spin ground state with a predominant uniaxial anisotropy. The quantum nature of these systems makes them very appealing for phenomena occurring on the mesoscopic scale, i.e., at the boundary between classical and quantum physics. Below their blocking temperature, they exhibit magnetisation hysteresis, the classical macroscale property of a magnet, as well as quantum tunnelling of magnetisation and quantum phase interference, the properties of a microscale entity. Quantum effects are advantageous for some potential applications of single-molecule magnets, e.g., in providing the quantum superposition of states for quantum computing, but are a disadvantage in others such as information storage. It is believed that single-molecule magnets have a potential for quantum computation, in particular because they are extremely small and almost identical, allowing to obtain, in a single measurement, statistical averages of a larger number of qubits. This review introduces some basic concepts that are needed to understand the quantum phenomena observed in molecular nanomagnets and discusses new trends of the field of molecular nanomagnets towards molecular spintronics.