Spin Induced Quantum Tunneling of the Magnetization

Abstract

Quantum tunneling of the magnetization (QTM) of the spin-1/2 Vanadium-15 (V[Formula: see text] single molecular magnets (SMMs) is investigated by means of the effective field theory developed by Kaneyoshi. We deal with the two hexagon layers (shell, V[Formula: see text] and one triangular interlayer (core, V[Formula: see text] with the spin-1/2 Ising particles. We find that the V[Formula: see text] has a normal ferromagnetic hysteresis behavior for its all spins are up (parallel). However, V[Formula: see text] has a staircase-like hysteresis behavior that is the signature of the QTM for the spin-down orientation (antiparallel) of the core. QTM appears with the splitting of the magnetizations versus temperature ([Formula: see text]–[Formula: see text] and external field ([Formula: see text]–[Formula: see text] curves. Namely, QTM occurs from [Formula: see text] to [Formula: see text] in the core, from +[Formula: see text] to [Formula: see text] [Formula: see text] in the shell (only [Formula: see text]–[Formula: see text] curves at [Formula: see text] 0.1) and from [Formula: see text] to [Formula: see text] [Formula: see text] in the total V[Formula: see text]. By considering these different splitting behaviors of the magnetizations of the shell, core and total [Formula: see text] at [Formula: see text] and [Formula: see text], we suggest three different kinds of QTM: 1-ferromagnetic QTM (FMQTM) at [Formula: see text] for the shell, 2-antiferromagnetic QTM (AFMQTM) at [Formula: see text] for the core and 3-paramagnetic QTM (PMQTM) at [Formula: see text] for the shell, core and total V[Formula: see text] SMM. Moreover, it is found that there is a relationship between the QTM and type II and surface superconductivity. The EFT results of QTM in V[Formula: see text] are in good agreement with the other theoretical and experimental results of the V[Formula: see text] and other SMMs.