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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Chemical Bonding Governs Complex Magnetism in MnPt 5 P

Subtle changes in chemical bonds may result in dramatic revolutions in magnetic properties in solid-state materials. MnPt 5 P, a derivative of the rare-earth-free ferromagnetic MnPt 5 As, was discovered and is presented in this work. Specifically, MnPt 5 P was synthesized, and its crystal structure and chemical composition were characterized by X-ray diffraction as well as energy-dispersive X-ray spectroscopy. Accordingly, MnPt 5 P crystallizes in the layered tetragonal structure with the space group P4/mmm (No. 123), in which the face-shared Mn@Pt 12 polyhedral layers are separated by P layers. In contrast to the ferromagnetism observed in MnPt 5 As, the magnetic properties measurements on MnPt 5 P show antiferromagnetic ordering occurs at ~188 K with a strong magnetic anisotropy in and out of the ab-plane. Moreover, a spin-flop transition appears when a high magnetic field is applied. An A-type antiferromagnetic structure was obtained from the analysis of powder neutron diffraction (PND) patterns collected at 150 and 9 K. Calculated electronic structures imply that hybridization of Mn-3d and Pt-5d orbitals is critical for both the structural stability and observed magnetic properties. Semiempirical molecular orbitals calculations on both MnPt 5 P and MnPt 5 As indicate that the lack of 4p character on the P atoms at the highest occupied molecular orbital (HOMO) in MnPt 5 P may cause the different magnetic behavior in MnPt 5 P compared to MnPt 5 As. The discovery of MnPt 5 P, along with our previously reported MnPt5As, parametrizes the end points of a tunable system to study the chemical bonding which tunes the magnetic ordering from ferromagnetism to antiferromagnetism with the strong spin–orbit coupling (SOC) effect.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on MnPt(CN)6 by Materials Project

MnPt(CN)6 is alpha Rhenium trioxide-derived structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mn2+ is bonded in an octahedral geometry to six equivalent N3- atoms. All Mn–N bond lengths are 1.94 Å. Pt2- is bonded in an octahedral geometry to six equivalent C3+ atoms. All Pt–C bond lengths are 2.02 Å. C3+ is bonded in a linear geometry to one Pt2- and one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a linear geometry to one Mn2+ and one C3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnPt by Materials Project

PtMn is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Mn2+ is bonded in a body-centered cubic geometry to eight equivalent Pt2- atoms. All Mn–Pt bond lengths are 2.72 Å. Pt2- is bonded in a body-centered cubic geometry to eight equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnPt by Materials Project

PtMn crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Mn2+ is bonded in a distorted hexagonal planar geometry to six equivalent Pt2- atoms. All Mn–Pt bond lengths are 2.66 Å. Pt2- is bonded to six equivalent Mn2+ atoms to form a mixture of distorted edge and corner-sharing PtMn6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Mn(Pt 1–x Pd x ) 5 P: Isovalent tuning of Mn-sublattice magnetic order

Here, e report the growth and characterization of MnPd 5 P, a rare-earth-free ferromagnet, with T C ≈ 295 K and planar anisotropy, and conduct a substitutional study with its antiferromagnetic analogue MnPt 5 P. We provide a solution route to grow large single crystals of MnPd 5 P and the series Mn(Pt 1–x Pd x ) 5 P by adding Mn into Pd-P and (Pt 1–x Pd x )-P based melts. All compounds in the family adopt the layered anti-CeCoIn5 type structure with the space group P4/mmm, and EDS and X-ray diffraction results indicate that MnPt 5 P and MnPd 5 P form a complete solid solution. Based on measurements of the temperature- and field-dependent magnetization and resistance, we construct a temperature-composition (T-x) phase diagram for Mn(Pt 1–x Pd x ) 5 P and demonstrate that the initial antiferromagnetic order found in MnPt 5 P is extraordinarily sensitive to Pd substitution. At low Pd fractions (x < 0.010), the single antiferromagnetic transition in pure MnPt 5 P splits into a higher temperature ferromagnetic transition followed first, upon cooling, by a lower temperature ferromagnetic to antiferromagnetic transition and then by a re-entrant antiferromagnetic to ferromagnetic transition at even lower temperatures. The antiferromagnetic region makes up a bubble phase that persists up to x ≈ 0.008-0.009 for T ≈ 150 K, with all samples x < 0.008 recovering their initial ferromagnetic state upon further cooling to base temperature. Over the same low substitution range we find a non-monotonic change in the room temperature value of the unit cell volume, further suggesting that pure MnPt 5 P is very close to an instability. Once x > 0.010, Mn(Pt 1–x Pd x ) 5 P undergoes a only single transition into the ferromagnetic phase. The Curie temperature initially increases rapidly with x, rising from T C ≈ 197 K at x = 0.013 to a maximum of T C ≈ 312 K for x ≈ 0.62, and then falling back to T C ≈ 295 K for pure MnPd 5 P (x = 1.00). Given that Pt and Pd are isoelectronic, this work raises questions as to the origin of the extreme sensitivity of the magnetic ground state in MnPt 5 P upon introducing Pd.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Magnetic compressibility of layered ferromagnet under pressure

This study systematically investigates the magnetic properties of the layered ferromagnet MnPt 5 As under pressure through a combination of experimental measurements and theoretical simulations. MnPt 5 As exhibits a ferromagnetic transition at approximately 301 K. Neutron diffraction measurements under applied pressures up to ∼4.9 GPa were performed over a temperature range from 320 to 100 K to probe its magnetic behavior. The results confirm that the Mn atoms maintain a ferromagnetic order under applied pressures, consistent with the ambient-pressure findings. However, magnetic anisotropy is notably suppressed. To further elucidate the compressibility of magnetic anisotropy in MnPt 5 As, x-ray diffraction under pressure was conducted. The results reveal that the c-axis undergoes a greater and more rapid compression compared to the ab -plane, which may contribute to the observed suppression of Mn ferromagnetic ordering along the c -axis. Additionally, theoretical calculations indicate that magnetic ordering exhibits a similar pressure-induced trend under applied pressure, supporting the experimental observations. These findings offer insights into the pressure-dependent magnetic properties and anisotropy of MnPt 5 As, with potential implications for strain engineering in Mn-based magnetic devices.

Electronic band structure↗
DOE OSTI2020

Interfacial Dzyaloshinskii-Moriya interaction of antiferromagnetic materials

The interface between a ferromagnet (FM) or antiferromagnet (AFM) and a heavy metal (HM) results in an antisymmetric exchange interaction known as the interfacial Dzyaloshinskii-Moriya interaction (iDMI) which favors non-collinear spin configurations. The iDMI is responsible for stabilizing noncollinear spin textures such as skyrmions in materials with bulk inversion symmetry. Interfacial DMI values have been previously determined theoretically and experimentally for FM/HM interfaces, and, in this work, they are calculated for the metallic AFM MnPt and the insulating AFM NiO. The heavy metals considered are W, Re, and Au. Values for the iDMI, exchange, and anisotropy constants are determined for different AFM and HM thicknesses. The iDMI values of the MnPt heterolayers are comparable to those of the common FM materials, and those of NiO are lower. In few-layer films of (001) MnPt, the high spin orbit coupling of the Pt layers can give rise to a small DMI in the absence of a HM layer.

36 MATERIALS SCIENCE↗