Superparamagnetic and superspin glass behaviors in the martensitic state of Ni43.5Co6.5Mn39Sn11 magnetic shape memory alloy

Abstract

The magnetic state of the low-temperature martensite in a Ni43.5Co6.5Mn39Sn11 magnetic shape memory alloy (MSMA) is disclosed. At temperatures (T) above a critical temperature Tf, the magnetization versus field [M(H)] curves display a sigmoid shape, show no magnetic hysteresis, and can be well fitted according to the Langevin model, confirming that the martensite shows superparamagnetic behavior at T>Tf. On the other hand, the observation of a memory effect during the stop-and-wait protocol and the analysis of dynamic magnetic properties probed by ac susceptibility measurements unequivocally corroborate the superspin glass behavior of interacting magnetic clusters at T<Tf. The present study provides significant insights into the magnetism of martensite in MSMAs.

Sequence of structural and magnetic transitions in Ni48Co2Mn39Sn11 shape memory alloy

“…Different magnetic behaviors including paramagnetic [25], antiferromagnetic [26], and reentrant spin glass [27] behaviors have been reported in the literature. Recently, we also observed SPM and SSG behaviors in the martensitic state of a Ni 43.5 Co 6.5 Mn 39 Sn 11 alloy [12]; the SPM martensite of that alloy is directly transformed from the ferromagnetic austenite, and a transition sequence of ferromagnetic austenite-SPM martensite -SSG martensite is followed. Nevertheless, it remained an open question whether the SPM and SSG behaviors of martensite are unique only in that particular alloy.…”

“…The lack of information on these aspects has greatly hindered further attempts to optimize the functional properties of these alloys. Quite recently, we investigated the magnetic properties of martensite in a Ni 43.5 Co 6.5 Mn 39 Sn 11 MSMA [12]. However, as the phase transformation and magnetic properties of the Ni-Co-Mn-Sn alloys are highly sensitive to their chemical composition, alloys with different composition should be studied in order to gain a comprehensive understanding of the structural and magnetic transitions in this alloy system.…”

Magnetoresistance of Cu–Mn–Al melt-spun ribbons containing the system of interacting ferromagnetic inclusions

“…Although the breakthrough in spintronics was achieved due to multilayer structures, granular materials based on the Heusler alloys have also been thoroughly studied as potential spin-injector materials. The experimental investigation of their electronic transport and magnetostructural transitions [1][2][3][4][5] as well as theoretical models and calculations predicting the effects of the spin-polarized medium [6][7][8][9] is presented in numerous works. They have shown that the magnetic and transport properties of the granular materials are defined by a combination of different factors such as preparation and treatment conditions, and the choice of the matrix compounds, as well as combinations of the interparticle distance, size and magnetic moments of particles.…”

Small-angle neutron scattering study of magnetic ordering and inhomogeneity across the martensitic phase transformation in Ni50−xCoxMnBhatti1, El-Khatib2, Srivastava3 et al. 2012Phys. Rev. B

“…the issue of whether the background martensitic matrix is in fact paramagnetic or AF, the spatial range of the F and AF spin correlations, and the true nature of the freezing transition. Regarding the latter issue, it has been suggested, by a number of authors [19,20], that the freezing of the spin clusters is actually collective, obviously requiring strong inter-cluster interactions, leading to a so-called "super-spinglass" state. Additionally, it is now clear, from a number of works [e.g.…”