Spins Of Magnetic Ions, Coupled Via The Exchange Interaction, Ferromagnetic State Breaks The Mirror Symmetry Of The Ising Chain, While The Paramagnetic One Does Not, Nuclear Spin-Lattice Relaxation, Spin Fluctuations Are Expected To Exhibit The Energy Gap

Abstract

A single-molecule magnet placed in a magnetic field perpendicular to its anisotropy axis can be truncated to an effective two-level system, with easily tunable energy splitting. The quantum coherence of the molecular spin is largely determined by the dynamics of the surrounding nuclear spin bath. Here A. Morello, A. Millán, and L. J. de Jongh report the measurement of the nuclear spin-lattice relaxation rate 1/T1n in a single crystal of the single-molecule magnet Mn12-ac, at T≈30 mK in perpendicular fields B⊥ up to 9 T. The relaxation channel at B≈0 is dominated by incoherent quantum tunneling of the Mn12-ac spin S, aided by the nuclear bath itself. However for B⊥>5 T we observe an increase of 1/T1n by several orders of magnitude up to the highest field............

The full paper: http://www.iiste.org/PDFshare/APTA-PAGENO-366610-370723.pdf