Intrinsic magnetic properties of bimetallic nanoparticles elaborated by cluster beam deposition

Abstract

In this paper, we present some specific chemical and magnetic order obtained very recently on characteristic bimetallic nanoalloys prepared by mass-selected Low Energy Cluster Beam Deposition (LECBD). We study how the competition between d-atom hybridization, complex structure, morphology and chemical affinity affects their intrinsic magnetic properties at the nanoscale. The structural and magnetic properties of these nanoalloys were investigated using various experimental techniques that include High Resolution Transmission Electron Microscopy (HRTEM), Superconducting Quantum Interference Device (SQUID) magnetometry, as well as synchrotron techniques such as Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Magnetic Circular Dichroism (XMCD). Depending on the chemical nature of the nanoalloys we observe different magnetic responses compared to their bulk counterparts. In particular, we show how specific relaxation in nanoalloys impacts their magnetic anisotropy; and how finite size effects (size reduction) inversely enhance their magnetic moment.

Cubic chemically ordered FeRh and FeCo nanomagnets prepared by mass-selected low-energy cluster-beam deposition: a comparative study

“…Briefly, a pulsed laser beam is focused on a mixed equiatomic target while a continuous flow of helium allows the formation of the cluster beam. After isentropic expansion in vacuum, ionized species can be size-selected thanks to a quadupolar electrostatic deviator [4]. Then, the mass-selected clusters are simultaneously co-deposited in an ultra-high vacuum (UHV) deposition chamber, with an independent atomic carbon beam.…”

“…First, the magnetic properties of Fe-based clusters embedded in a carbon matrix have been studied by superconducting quantum interference device (SQUID) magnetometry experiments and simulations [4,19–21]. …”

“…Notice that metamagnetic transitions in bulk B2 FeRh are expected from the anti-ferromagnetic (AFM) to the ferromagnetic (FM) state at 96 °C and to the paramagnetic (PM) state at 380 °C. (b) Bulk FeCo phase diagram showing the different chemical and crystallographic orders for equiatomic concentration (adapted from [4]).…”

“…Notice that most of this work is based on the results of the PhD theses of A. Hillion [10] and G. Khadra [11] at Lyon, France. The structural and magnetic properties of as-prepared and annealed nanoalloys were investigated using various experimental techniques [4]. Here, we focus on anomalous X-rays diffraction (AXD) and X-ray magnetic circular dichroism (XMCD) performed by using well-adapted synchrotron radiation beamlines.…”

Phase separation and surface segregation in Co–Au–SrTiO3 thin films: Self-assembly of bilayered epitaxial nanocolumnar composites

“…However, the simultaneous tuning of these parameters in assemblies of ultrasmall immiscible nanoalloys has remained elusive so far. Phase segregated Co-Au nanostructures reported in literature are generally spherical [6][7][8]. In contrast, nanostructures obtained by filling nanopores display shape anisotropy but usually exhibit poor crystallinity [9].…”