Crystal Structure, Magnetism, and Electronic Properties of a Rare-Earth-Free Ferromagnet: MnPt5As

Xin Gui,Weiwei Xie

doi:10.1021/acs.chemmater.0c00244

Abstract

The design and synthesis of targeted functional materials have been a long-term goal for material scientists. Although a universal design strategy is difficult to generate for all types of materials, however, it is still helpful for a typical family of materials to have such design rules. Herein, we incorporated several significant chemical and physical factors regarding magnetism, such as structure type, atom distance, spin-orbit coupling, and successfully synthesized a new rare-earth-free ferromagnet, MnPt5As, for the first time. MnPt5As can be prepared by using high-temperature pellet methods. According to X-ray diffraction results, MnPt5As crystallizes in a tetragonal unit cell with the space group P4/mmm (Pearson symbol tP7). Magnetic measurements on MnPt5As confirm ferromagnetism in this phase with a Curie temperature of ~301 K and a saturated moment of 3.5 uB per formula. Evaluation by applying the Stoner Criterion also indicates that MnPt5As is susceptible to ferromagnetism. Electronic structure calculations using the WIEN2k program with local spin density approximation imply that the spontaneous magnetization of this phase arises primarily from the hybridization of d orbitals on both Mn and Pt atoms. The theoretical assessments are consistent with the experimental results. Moreover, the spin-orbit coupling effects heavily influence on magnetic moments in MnPt5As. MnPt5As is the first high-performance magnetic material in this structure type. The discovery of MnPt5As offers a platform to study the interplay between magnetism and structure.

Highlights

How one can approach new ferromagnetic materials, especially to induce high transition temperatures and high saturated moments, is a demanding necessity for materials synthetic materials scientists
The exploration of ferromagnetic intermetallic materials without strategically vulnerable rare-earth elements is critical for information technology applications, such as magnetic and magnetoelastic sensors,[1] hard-disk drives,[2] spintronics,[3−5] and biomedical devices.[6]
An anomaly can be observed around 300 K, which reflects the ferromagnetic ordering transition, similar to other ferromagnetic intermetallics, for example, Ce2CoGe3, Ce5Co4Ge13, and Y(Fe1−xCox)2.55,5655,56 The reason for the kink observed could be that the major contribution of resistivity in MnPt5As changes from electron−phonon scattering to electron−electron scattering while it is possible that additional magnetoresistance contribution develops below Tc

Summary

Introduction

How one can approach new ferromagnetic materials (e.g., create a practical design strategy), especially to induce high transition temperatures and high saturated moments, is a demanding necessity for materials synthetic materials scientists. The small coercivity (∼15 Oe at 1.8 K) confirms the soft ferromagnetic character of MnPt5As. Figure 3a shows the field dependences of the magnetization per Mn atom.

Results

Conclusion