4 research outputs found
Magnetic order and phase transitions in Fe Pt Rh
Polarized and unpolarized neutron diffraction techniques have been applied to study the temperature-dependent magnetic and structural properties of four 200 nm-thick Fe50Pt50-xRhx films with x = 5, x = 10, x = 17.5 and x = 25. Similar to the bulk system, an antiferromagnetic to ferromagnetic transition can be found in the films with decreasing Rh concentration. The application of structure factor calculations enables one to determine the microscopic magnetic configuration of the different films as a function of temperature and Rh concentration. The developed models indicate a magnetic transition from a dominant antiferromagnetic order in the out-of-plane direction to a dominant ferromagnetic order in the in-plane direction with decreasing Rh concentration. The different magnetic configurations can theoretically be described by a phenomenological model which includes a two-ion and a one-ion interaction Hamiltonian term with different temperature dependencies of the anisotropy constants
Complex Three-Dimensional Magnetic Ordering in Segmented Nanowire Arrays
A comprehensive
three-dimensional picture of magnetic ordering
in high-density arrays of segmented FeGa/Cu nanowires is experimentally
realized through the application of polarized small-angle neutron
scattering. The competing energetics of dipolar interactions, shape
anisotropy, and Zeeman energy in concert stabilize a highly tunable
spin structure that depends heavily on the applied field and sample
geometry. Consequently, we observe ferromagnetic and antiferromagnetic
interactions both among wires and between segments within individual
wires. The resulting magnetic structure for our nanowire sample in
a low field is a fan with magnetization perpendicular to the wire
axis that aligns nearly antiparallel from one segment to the next
along the wire axis. Additionally, while the low-field interwire coupling
is ferromagnetic, application of a field tips the moments toward the
nanowire axis, resulting in highly frustrated antiferromagnetic stripe
patterns in the hexagonal nanowire lattice. Theoretical calculations
confirm these observations, providing insight into the competing interactions
and resulting stability windows for a variety of ordered magnetic
structures. These results provide a roadmap for designing high-density
magnetic nanowire arrays for spintronic device applications