Macroscopic quantum tunneling of magnetization explored by quantum-first-order reversal curves

Abstract

A novel method to study the fundamental problem of quantum double well potential systems that display magnetic hysteresis is proposed. The method, coined quantum-first-order reversal curve (QFORC) analysis, is inspired by the conventional first-order reversal curve (FORC) protocol, based on the Preisach model for hysteretic phenomena. We successfully tested the QFORC method in the peculiar hysteresis of the Mn 12 Ac molecular magnet, which is governed by macroscopic quantum tunneling of magnetization. The QFORC approach allows one to quickly reproduce well the experimental magnetization behavior, and more importantly to acquire information that is difficult to infer from the usual methods based on matrix diagonalization. It is possible to separate the thermal activation and tunneling contributions from the magnetization variation, as well as understand each experimentally observed jump of the magnetization curve and associate them with specific quantum transitions.

Time resolved FORC analysis and magnetic anisotropy in K0.4[Cr(CN)6][Mn(S)-pn] (S)-pnH0.6 chiral molecular magnets

“…Since the ratio of continuous and jump relaxations is close to 1, it would be important to establish a contribution of reversal magnetization jumps to the FORC diagram. A similar problem appeared and was solved for the single molecule Mn 12 Ac magnet [38], where central FORC maxima were caused by magnetization jumps. Although Mn 12 Ac magnet does not demonstrate long-range ferromagnetism, we use the same experimental method to verify magnetization jumps contribution.…”

“…A contribution of magnetization jumps to magnetic relaxation and continuous reversal magnetization were observed and analyzed in [6,38]. Since the ratio of continuous and jump relaxations is close to 1, it would be important to establish a contribution of reversal magnetization jumps to the FORC diagram.…”

doFORC tool for calculating first-order reversal curve diagrams of noisy scattered data

“…The conjointly use of several experimental and modeling techniques is the current state-of-the-art in the quantitative FORC technique which already has offered profound physical insight in the study of many magnetic systems like the magnetic nanowire arrays, [12][13][14][15][16] magnetic wires, 17 antidote lattices, 18 magnetic bilayer ribbons, 19 nanostrips, 20 hard/soft bilayer magnetic antidots, 21 magnetic multilayer systems, 22,23 and even in molecular magnets at very low temperatures. 24 Many other such valuable studies could be mentioned in the last few years alone.…”