Chemical Bonding Governs Complex Magnetism in MnPtP.

Subtle changes in chemical bonds may result in dramatic revolutions in magnetic properties in solid-state materials. MnPtP, a derivative of the rare-earth-free ferromagnetic MnPtAs, was discovered and is presented in this work. MnPtP was synthesized, and its crystal structure and chemical composition were characterized by X-ray diffraction as well as energy-dispersive X-ray spectroscopy. Accordingly, MnPtP crystallizes in the layered tetragonal structure with the space group 4/ (No. 123), in which the face-shared Mn@Pt polyhedral layers are separated by P layers. In contrast to the ferromagnetism observed in MnPtAs, the magnetic properties measurements on MnPtP show antiferromagnetic ordering occurs at ∼188 K with a strong magnetic anisotropy in and out of the -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-3 and Pt-5 orbitals is critical for both the structural stability and observed magnetic properties. Semiempirical molecular orbitals calculations on both MnPtP and MnPtAs indicate that the lack of 4 character on the P atoms at the highest occupied molecular orbital (HOMO) in MnPtP may cause the different magnetic behavior in MnPtP compared to MnPtAs. The discovery of MnPtP, along with our previously reported MnPtAs, 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.