Suppression of Ferromagnetism in Single Crystal Nanowire Array of MnPt3

Though physical confinement of magnetic materials can profoundly modify their properties and is necessary for applications, there is limited understanding of the underlying mechanisms. Nanoscale confinement can significantly impact the spin textures, domain structures, and collective excitations of magnetic materials with ordered bulk states. Upon physical confinement to tens of nanometers, the symmetry-breaking surface energy becomes a dominant factor, altering the effective magnetic interactions, while discretizing the spin-wave spectrum. Single-crystalline magnetic nanowires, with only one macroscopic dimension, offer a robust controlled platform to study such effects while enabling targeted manipulation of magnetic states relevant to advanced spintronics functionalities. In the bulk form the cubic intermetallic ferromagnet MnPt₃ (T_c = 390K) has been found to display an AHE, and is thought to have potential applications in spintronics. The bulk magnon dispersion relation has been established before with inelastic neutron inelastic scattering. We have made arrays of single-crystalline MnPt₃ nanowires with diameters ranging from 20 nm to 120 nm embedded in anodized Al₂O₃ mold with thermomechanical nanomolding. Magnetization measurements reveal a pronounced suppression of magnetic order with decreasing nanowire diameter: a one-point-five reduction from 4.2 Bohr magneton/f.u. between the polycrystalline bulk and 120 nm-diameter nanowires, and a ten-fold suppression of order at diameters of less than 80 nm, indicating profound impacts of the Al₂O₃ interface through this length scale.