Quasistatic remanence in Dzyaloshinskii-Moriya interaction driven weak ferromagnets and piezomagnets

Abstract

We explore remanent magnetization (µ) as a function of time and temperature, in a variety of rhombohedral antiferromagnets (AFM) which are also weak ferromagnets (WFM) and piezomagnets (PzM). These measurements, across samples with length scales ranging from nano to bulk, firmly establish the presence of a remanence that is quasi static in nature and exhibits a counter-intuitive magnetic field dependence. These observations unravel an ultra-slow magnetization relaxation phenomenon related to this quasi static remanence. This feature is also observed in a defect free single crystal of α-Fe2O3, which is a canonical WFM and PzM. Notably, α-Fe2O3 is not a typical geometrically frustrated AFM and in single crystal form, it is also devoid of any size or interface effects, which are the usual suspects for a slow magnetization relaxation phenomenon. The underlying pinning mechanism appears exclusive to those AFM which are either symmetry allowed WFM, driven by Dzyaloshinskii-Moriya Interaction (DMI) or can generate this trait by tuning of size and interface. The qualitative features of the quasi static remanence indicate that such WFM are potential piezomagnets, in which magnetization can be tuned by stress alone. arXiv:1703.09075v2 [cond-mat.str-el]

Phenomenology of chiral Dzyaloshinskii-Moriya interactions in strained materials

“…Finally, we provide examples of two relevant strain fields which can lead to cDM interactions in intrinsically DM-inactive materials. Our analysis expands upon previous reports of strain and geometry-coupled magnetic phenomena [18][19][20][21][22][23][24], and provides a general roadmap for controlling chiral magnetic interactions via strain in materials of all symmetries.…”

Weak ferromagnetism andtime-stable remanencein hematite: effect of shape, size and morphology

“…However, in this work our focus is on exploring the effect of morphology on the remanent magnetization or remanence in hematite. We have earlier observed a unique remanence in not only a number of symmetry allowed WFM/PzM, including a single crystal * ashna@iiserpune.ac.in hematite [26], but also in some isostructural systems wherein this effect arises due to size and interface [27,28]. We have also established that the remanance in these canted AFM has some unique footprints [26], which sets it apart from any other conventional or complex magnetic systems [29][30][31][32][33][34].…”

“…Thus heating cooling cycles as well as the magnitude of H applied during magnetization measurements profoundly effects the number of WFM domains, which accordingly reflect in the magnitude of time-stable part of remanence. This also relates to a unique pinning mechanism [26]. In case of the porous sample, the peak like effect in µ vs H is sharper (smaller FWHM) as compared to all other morphologies of the hematite.…”

“…We have earlier observed a unique remanence in not only a number of symmetry allowed WFM/PzM, including a single crystal * ashna@iiserpune.ac.in hematite [26], but also in some isostructural systems wherein this effect arises due to size and interface [27,28]. We have also established that the remanance in these canted AFM has some unique footprints [26], which sets it apart from any other conventional or complex magnetic systems [29][30][31][32][33][34]. Here the key observation has been an ultra-slow magnetization relaxation phenomenon, resulting in the observation of a timestable remanence, hereafter reffered to as µ. Hematite is also a unique compound as it exhibits both AFM and WFM phase as a function of temperature [2].…”

“…Here the key observation has been an ultra-slow magnetization relaxation phenomenon, resulting in the observation of a timestable remanence, hereafter reffered to as µ. Hematite is also a unique compound as it exhibits both AFM and WFM phase as a function of temperature [2]. Interestingly, the time-stable remanence appears in the WFM phase but it is negligibly small in its pure AFM state, as is observed in single crystal of hematite [26].…”