Entropy-reduced retention times in magnetic memory elements: A case of the Meyer-Neldel Compensation Rule

TL;DR

This paper investigates the thermally-activated magnetization reversal times in magnetic memory elements, revealing that the Arrhenius prefactor varies significantly with material parameters and follows the Meyer-Neldel rule, challenging traditional assumptions.

Contribution

It demonstrates that the Arrhenius prefactor in magnetic memory elements can be extremely large and energy-dependent, illustrating a case of the Meyer-Neldel compensation rule in magnetic switching.

Findings

Prefactor can reach up to 10^21 Hz

Prefactor varies exponentially with activation energy

Modeling with a constant prefactor is inadequate

Abstract

We compute mean waiting times between thermally-activated magnetization reversals in a nanodisk with parameters similar to a free CoFeB layer used in magnetic random access memories. By combining Langer's theory and forward flux sampling simulations, we show that the Arrhenius prefactor can take values up to 10$^{21}$ Hz, orders of magnitude beyond the value of 10$^{9}$ Hz typically assumed, and varies drastically as a function of material parameters. We show that the prefactor behaves like an exponential of the activation energy, which highlights a case of the Meyer-Neldel compensation rule. This suggests that modeling information retention times with a barrier-independent prefactor in such magnetic storage elements is not justified.