Time-dependent spintronic anisotropy in magnetic molecules

TL;DR

This paper investigates the real-time dynamical response of magnetic molecules coupled to ferromagnetic leads during a quench, revealing how anisotropy and Kondo correlations evolve with coupling strength, temperature, and molecule size.

Contribution

It introduces a detailed theoretical analysis of spin-dependent quench dynamics in large-spin magnetic molecules using advanced numerical methods, highlighting the effects of temperature and lead polarization.

Findings

Transient anisotropy dynamics depend on coupling strength and temperature.

Finite temperature suppresses the spin-quadrupole moment significantly.

Large molecule spins exhibit similar dynamical behaviors as smaller spins.

Abstract

We theoretically study the quench dynamics of induced anisotropy of a large-spin magnetic molecule coupled to spin-polarized ferromagnetic leads. The real-time evolution is calculated by means of the time-dependent density-matrix numerical renormalization group method implemented within the matrix product states framework, which takes into account all correlations in very accurate manner. We determine the system's response to a quench in the spin-dependent coupling to ferromagnetic leads. In particular, we focus on the transient dynamics associated with crossing from the weak to the strong coupling regime, where the Kondo correlations become important. The dynamics is examined by calculating the time-dependent expectation values of the spin-quadrupole moment and the associated spin operators. We identify the relevant time scales describing the quench dynamics and determine the influence of the molecule's effective exchange coupling and leads spin-polarization on the dynamical behavior of the system. Furthermore, the generalization of our predictions for large values of molecule's spin is considered. Finally, we analyze the effect of finite temperature and show that it gives rise to a reduction of magnetic anisotropy by strong suppression of the time-dependent spin-quadrupole moment due to thermal fluctuations.