Magnetic Characterization of Electrodeposited Pt_1−xNi_x Alloy Films: Influence of Deposition Potential and the Presence of Boric Acid

Abstract

Pt1-xNix (x = 0.25 to 0.92) thin films were examined for possible application as magnetic thermometers. The alloys were prepared by potentiostatic electrodeposition from aqueous chloride-based solutions in the presence and absence of 0.5 mol dm−3 B(OH)3. Alloy composition was controlled by the deposition potential with the Ni concentration increasing towards more reducing potentials. Films with x > 0.45 were ferromagnetic with the magnetization at 300 K increasing with nickel content. Magnetization vs temperature (M vs T) at 8 kA m−1 (100 Oe) showed an increase in the Curie temperature from less than 200 K to above 400 K for the alloys investigated. For films deposited at potentials >−0.6 V vs the saturated calomel electrode (SCE), boric acid had negligible effect on the magnetization at the maximum applied field in M vs H measurements. In contrast, for depositions at more reducing potentials <−0.6 V vs SCE the presence of boric acid resulted in diminished magnetization. This effect was attributed to elevated incorporation of oxygen (up to ∼4 atomic %), along with boron incorporation of about 400 μmol mol−1.

Dealloyed Pt74Ni26 and Pt26Ni74 Electrodeposited Thin Film Electrocatalysts for Oxygen Reduction

“…A slight negative displacement from Vegard's law was observed, though a range of deviations can be found in the literature. 52,54 This deviation may be at least partly attributed to some combination of the in-plane tensile stress, that in the present work corresponds to lattice compression along the surface normal sampled by symmetric XRD, 46 electronic effects, chemical disorder effects, 54 co-deposited H, or possibly a systematic error in the XEDS composition measurement. Coherence lengths were determined to be ≈9 nm for Pt 74 Ni 26 and ≈7 nm for Pt 26 Ni 74 from XRD peak widths using Scherrer's equation that convolves contributions from both the small grain size and microstrain.…”

“…1. 28,29,45,46,50,52 Deposition times for this series were chosen using prior knowledge of the current efficiency 45,46 to obtain an approximate 500 nm film thickness for all samples in the series. XRD revealed the films to be face-centered cubic (fcc) alloys with a lattice parameter that increased monotonically with increasing deposition potential.…”

“…28,29 The dispersion in observed shrinkage may reflect not only variations in the dealloying procedures but also differences in the film thickness of the as-deposited material due to tertiary current distribution associated with mixed control electrodeposition under free convection. Examples of such thickness variations during deposition under quiescent conditions have been previously articulated 52 and an example is provided in Fig. S8.…”

Thermosensitivity through Exchange Coupling in Ferrimagnetic/Antiferromagnetic Nano-Objects for Magnetic-Based Thermometry

“…Thermosensitivity is a change in magnetization with temperature, but this needs to be defined more clearly to compare materials. Using the definition from thermometry, 39,40 but replacing the changing property of resistance with magnetization, 41 we get the following…”

“…Thermosensitivity is a change in magnetization with temperature, but this needs to be defined more clearly to compare materials. Using the definition from thermometry, , but replacing the changing property of resistance with magnetization, we get the following where M is magnetization and T is temperature. However, it is important to note that thermosensitivity is only one parameter that will affect the performance of a material for T-MPI.…”