Bonding and Suppression of a Magnetic Phase Transition in EuMn₂P₂

Abstract

Electrons in solids often adopt complex patterns of chemical bonding driven by the competition between energy gains from covalency and delocalization, and energy costs of double occupation to satisfy Pauli exclusion, with multiple intermediate states in the transition between highly localized, and magnetic, and delocalized, and nonmagnetic limits. Herein, we report a chemical pressure-driven transition from a proper Mn magnetic ordering phase transition to a Mn magnetic phase crossover in EuMn 2 P 2 the limiting end member of the EuMn 2 X 2 (X = Sb, As, P) family of layered materials. This loss of a magnetic ordering occurs despite EuMn 2 P 2 remaining an insulator at all temperatures, and with a phase transition to long-range Eu antiferromagnetic order at T N ≈ 17 K. The absence of a Mn magnetic phase transition contrasts with the formation of long-range Mn order at T ≈ 130 K in isoelectronic EuMn 2 Sb 2 and EuMn 2 As 2 . Temperature-dependent specific heat and 31 P NMR measurements provide evidence for the development of short-range Mn magnetic correlations from T ≈ 250− 100 K, interpreted as a precursor to covalent bond formation. Density functional theory calculations demonstrate an unusual sensitivity of the band structure to the details of the imposed Mn and Eu magnetic order, with an antiferromagnetic Mn arrangement required to recapitulate an insulating state. Our results imply a picture in which long-range Mn magnetic order is suppressed by chemical pressure, but that antiferromagnetic correlations persist, narrowing bands and producing an insulating state.

Impact of Ge Doping on Structural and Magnetic Ordering in RMnxGa3 and R4Mn1–xGa12–yGey (R = Tb, Dy; x ≤ 0.25, y ≈ 1.0–3.3)

“…As there are compounds with 3d-metals, filled RGa 3 derivatives present an interesting case to study interactions between two magnetic subsystems, which can be quite complex. , The rare earth sublattice, in most cases, demonstrates antiferromagnetic ordering at low temperatures below 30 K, apart from some R 4 CrGa 12 compounds showing ferrimagnetic-like behavior . While transition metals apparently are not magnetically active in the most studied compounds, some manganese and iron compounds , were shown to demonstrate ferromagnetic ordering of the transition-metal sublattice.…”

Interplay between Magnetism and Topology: Large Topological Hall Effect in an Antiferromagnetic Topological Insulator, EuCuAs

“…Our room-temperature 151 Eu Mossbauer experiment (Figure 2c) confirms the divalent nature of Eu, i.e., Eu 2+ , as previously also observed in EuMn 2 P 2 . 36 The temperature-dependent longitudinal resistivity ρ xx of EuCuAs is shown in Figure 2b. From 300 to 50 K, ρ xx decreases linearly with decreasing temperature, indicating a metallic nature.…”

“…The short-range magnetic order contributions are prominent and visible up to temperatures above 2 T N . Our room-temperature 151 Eu Mössbauer experiment (Figure c) confirms the divalent nature of Eu, i.e., Eu 2+ , as previously also observed in EuMn 2 P 2 …”

Tools and Tricks for Single Crystal Growth

“…Several techniques for the synthesis of new materials, both common and uncommon, have been presented with a special focus on how each technique tackles the single crystal growth process differently and how variations on the established methods alter the standard process to enable and/or improve specific parts of the growth process. Additional synthetic techniques in the scientist’s toolkit provide improved flexibility − in the number of routes to approach the crystal growth of any one material, which can help synthesize single crystals of materials that might otherwise be unsuitable for certain techniques, and therefore improves the ability to target many more classes of materials for research. With greater visibility, it is hoped that greater usage and throughput for new and interesting materials in order to push forward on the many challenges facing society today will come.…”