Crossover temperature for quantum tunnelling in spin systems

3rd International School and Conference on Optoelectronics, Photonics, Engineering and Nanostructures (Saint Petersburg OPEN 2016)

Vlasov, S.M.^1,2 ; Bessarab, P.F.^3,4 ; Uzdin, V.M.^2,4 ; Jónsson, H.^1,5

Science Institute of the University of Iceland, Reykjavík, Iceland^1

Department of Natural Sciences, University ITMO, St. Petersburg

197101, Russia^2

Department of Materials and Nanophysics, Electrum 229, Royal Institute of Technology (KTH), Kista

SE-16440, Sweden^3

Department of Physics, St. Petersburg State University, St. Petersburg

198504, Russia^4

Department of Applied Physics, Aalto University, Espoo

FIN-00076, Finland^5

关键词: Activation mechanisms;    Analytical expressions;    Crossover temperature;    Energy surface;    Magnetic configuration;    Molecular magnet;    Quantum tunnelling;    Saddle point;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/741/1/012183/pdf
DOI  :  10.1088/1742-6596/741/1/012183

来源: IOP

【 摘 要 】

We derive an analytical expression for the crossover temperature corresponding to the transition from classical activation mechanism to temperature assisted quantum tunnelling in spin systems. The crossover temperature depends on the magnetic configuration and Hessian at the first order saddle point on the energy surface of the system. The theory is applied to several single spin models, including a system with four-fold anisotropy. Good agreement is obtained with experimental results for a molecular magnet containing Mn4.