Tunable Finite-Sized Chains to Control Magnetic Relaxation

TL;DR

This study demonstrates how the magnetic relaxation in low-dimensional iron ion chains can be controlled by adjusting the finite size of the chains in thin films, revealing size-dependent relaxation times while energy barriers remain constant.

Contribution

It introduces a method to tune magnetic relaxation times in finite-sized chains using thin film growth conditions, providing insights into finite-size effects in magnetic systems.

Findings

Energy barrier of 95 K is independent of chain length.

Single spin relaxation time increases with chain length from under 1 ps to 800 ps.

Thin films serve as a platform to study finite-size effects in magnetic relaxation.

Abstract

The magnetic dynamics of low-dimensional iron ion chains have been studied with regards to the tunable finite-sized chain length using iron phthalocyanine thin films. The deposition temperature varies the diffusion length during thin film growth by limiting the average crystal size in the range from 40 to 110 nm. Using a method common for single chain magnets, the magnetic relaxation time for each chain length is determined from temporal remanence data and fit to a stretched exponential form in the temperature range below 5 K, the onset for magnetic hysteresis. A temperature-independent master curve is generated by scaling the remanence by its relaxation time to fit the energy barrier for spin reversal, and the single spin relaxation time. The energy barrier of 95 K is found to be independent of the chain length. In contrast, the single spin relaxation time increases with longer chains from under 1 ps to 800 ps. We show that thin films provide the nano-architecture to control magnetic relaxation and a testbed to study finite-size effects in low-dimensional magnetic systems.