Chemical Bonding Governs Complex Magnetism in MnPt5P

Merging the AuCu3- and BaAl4-based structure motifs: flux-assisted synthesis, crystal, and electronic structure of Ca2Pt7XP4-δ phosphide platinides (X = Al, Ti, and Zn)

Three quaternary phosphide platinides, Ca₂Pt₇AlP_3.00(4), Ca₂Pt₇TiP_3.24(4), and Ca₂Pt₇ZnP_2.78(2), were synthesized by a high-temperature technique using lead as a flux. According to the single-crystal diffraction data, they are isotypic and crystallize in the tetragonal space group I4/mmm with Z = 2 (Ca₂Pt₇AlP_3.00(4): a = 3.9893(6) Å, c = 26.832(5) Å; Ca₂Pt₇TiP_3.24(4): a = 3.99610(10) Å, c = 26.9074(17) Å; Ca₂Pt₇ZnP_2.78(2): a = 4.0020(2) Å, c = 26.5549(17) Å) and thus represent first europium-free compounds of the Eu₂Pt₇AlP_2.95 structure type. Their structures can be described as an intergrowth of the AuCu₃- and CaBe₂Ge₂-type blocks. DFT calculations predict metallic conductivity and non-magnetic state for all three compounds. Bonding analysis based on the Bader charge distribution and ELF topology reveals a combination of localized covalent and ionic interactions in the CaBe₂Ge₂-type fragments and complex pattern of pairwise, multi-center, and ionic interactions in the AuCu₃-type fragments that closely reproduces bonding in the parent Pt₃X (X = Al, Ti, Zn) binary intermetallics.

Spin Reorientation in Antiferromagnetic MnPd5Se with an Anti-CeCoIn5 Structure Type

MnPd₅Se, a derivative of the anti-CeCoIn₅-type phase, was synthesized from a high-temperature solid-state reaction, structurally determined by X-ray diffraction, and magnetically characterized with a combined magnetic measurement and neutron powder diffraction (NPD). According to the X-ray diffraction results, MnPd₅Se crystallizes in a layered tetragonal structure with the same space group as CeCoIn₅, P4/mmm (No. 123). MnPd₅Se shows antiferromagnetic ordering around 80 K on the basis of the magnetic property measurements. An A-type antiferromagnetic structure was revealed from the analysis of neutron powder diffraction results at 300, 50, and 6 K. Moreover, a spin orientation rotation was observed as the temperature decreased. Pd L₃ X-ray absorption near edge spectroscopy results for MnPd₅Se semiqualitatively correlate with the calculated density of states supporting a nominal 0.2 electron transfer into the Pd d orbital from either Se or Mn in the compound. The discovery of MnPd₅Se, along with our previously reported MnT₅Pn (T = Pd or Pt; Pn = P or As), provides a tunable system for studying the magnetic ordering from ferromagnetism to antiferromagnetism with the strong spin-orbit coupling effect.