EP VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany.
Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
Phys Rev Lett. 2018 Apr 6;120(14):147202. doi: 10.1103/PhysRevLett.120.147202.
The magnetic properties of dilute Li_{2}(Li_{1-x}Fe_{x})N with x∼0.001 are dominated by the spin of single, isolated Fe atoms. Below T=10 K the spin-relaxation times become temperature independent indicating a crossover from thermal excitations to the quantum tunneling regime. We report on a strong increase of the spin-flip probability in transverse magnetic fields that proves the resonant character of this tunneling process. Longitudinal fields, on the other hand, lift the ground-state degeneracy and destroy the tunneling condition. An increase of the relaxation time by 4 orders of magnitude in applied fields of only a few milliTesla reveals exceptionally sharp tunneling resonances. Li_{2}(Li_{1-x}Fe_{x})N represents a comparatively simple and clean model system that opens the possibility to study quantum tunneling of the magnetization at liquid helium temperatures.
具有 x∼0.001 的稀 Li_{2}(Li_{1-x}Fe_{x})N 的磁性主要由单个孤立 Fe 原子的自旋决定。在 T=10 K 以下，自旋弛豫时间变得与温度无关，表明从热激发到量子隧穿区的转变。我们报告了在横向磁场中自旋翻转概率的强烈增加，这证明了该隧穿过程的共振特征。另一方面，纵向磁场消除了基态简并，并破坏了隧穿条件。在仅几毫特斯拉的外加场中，弛豫时间增加了 4 个数量级，这揭示了异常尖锐的隧穿共振。Li_{2}(Li_{1-x}Fe_{x})N 是一个相对简单和清洁的模型系统，为在液氦温度下研究磁化的量子隧穿开辟了可能性。
