Structure and magnetic properties of low-temperature phase Mn-Bi nanosheets with ultra-high coercivity and significant anisotropy

Abstract

The microstructure, crystal structure, and magnetic properties of low-temperature phase (LTP) Mn-Bi nanosheets, prepared by surfactant assistant high-energy ball milling (SA-HEBM) with oleylamine and oleic acid as the surfactant, were examined with scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. Effect of ball-milling time on the coercivity of LTP Mn-Bi nanosheets was systematically investigated. Results show that the high energy ball milling time from tens of minutes to several hours results in the coercivity increase of Mn-Bi powders and peak values of 14.3 kOe around 10 h. LTP Mn-Bi nanosheets are characterized by an average thickness of tens of nanometers, an average diameter of ∼1.5 μm, and possess a relatively large aspect ratio, an ultra-high room temperature coercivity of 22.3 kOe, a significant geometrical and magnetic anisotropy, and a strong (00l) crystal texture. Magnetization and demagnetization behaviors reveal that wall pinning is the dominant coercivity mechanism in these LTP Mn-Bi nanosheets. The ultrafine grain refinement introduced by the SA-HEBM process contribute to the ultra-high coercivity of LTP Mn-Bi nanosheets and a large number of defects put a powerful pinning effect on the magnetic domain movement, simultaneously. Further magnetic measurement at 437 K shows that a high coercivity of 17.8 kOe and a strong positive temperature coefficient of coercivity existed in the bonded permanent magnet made by LTP Mn-Bi nanosheets.

MnBi Magnetic Material: A Critical Review

“…The dependence i H c (D) was studied experimentally in [17][18][19][20], the results affirmed the above said tendency. By increasing the ball-milling times t m , the i H c of milled powders first increases, reaching a plateau and slightly drops when the grain size becomes smaller the domain size of ∼ 0.25 µm (see the inset of Fig.…”

Oleic acid/oleylamine ligand pair: a versatile combination in the synthesis of colloidal nanoparticles

“…The strong magnetic properties of these materials indicated their great potential for applications as high performance nanocomposite permanent magnets without the addition of any rare earth elements. 324…”

“…The strong magnetic properties of these materials indicated their great potential for applications as high performance nanocomposite permanent magnets without the addition of any rare earth elements. 324 Pd-Based NPs Among the Pd-magnetic metal NPs, Pd-Ni NPs have been investigated by many research groups due to their prominent electrocatalytic activity. The development of these bimetallic (or trimetallic) NPs has been achieved through various synthetic approaches, including electrodeposition and other physical and chemical methods.…”

Novel Anisotropic Magnetoelectric Effect on δ-FeO(OH)/P(VDF-TrFE) Multiferroic Composites

“…In the present work, the anisotropy of the ME response is obtained by the introduction of magnetic nanosheets of feroxyhyte (δ-FeO­(OH)) in a poly­[vinylidenefluoride- co -trifluoroethylene] (P­(VDF-TrFE)) piezoelectric matrix. The ME effect on the δ-FeO­(OH)/P­(VDF-TrFE) composites will not arise in the traditional way, by the coupling between the magnetostriction and piezoelectricity, but instead by the alignment of the feroxyhyte nanosheets, as a response to the applied magnetic field, on the P­(VDF-TrFE) matrix.…”