How to Obtain the Blocking Energy Barrier of a Co Adatom on a Single MgO Layer: A Theoretical Exploration

Co adatoms deposited on a single MgO layer have been reported to exhibit a record-high zero-field splitting of 58 meV (467.8 cm^-1). However, their effective blocking energy barrier is almost zero considering the much slower spin relaxation time on the order of 10^-4 s at 0.6 K induced by the significant quantum tunneling of magnetization (QTM) in the ground state (KD₀). Herein, we propose two viable strategies to obtain the energy barrier by enlarging the Co-O or Mg-O bond lengths, which leads to the decreased QTM in KD₀ arising from the nearest four Mg ions around Co. Thus, it is an effective way to obtain the energy barrier by utilizing substrates that feature longer bond lengths between the transition metal ions of Mg²⁺, Ca²⁺, K⁺, etc. and the O, C, N, etc. in practical applications.