Magnetic Properties Of Pt Research Articles

Bending strain–induced changes in perpendicular magnetic properties of Pt/Co/Pt films on flexible substrates

We studied the irreversible changes in the perpendicular magnetic properties of Pt(2.2 nm)/Co(0.8 nm)/Pt(2.2 nm) films deposited on a flexible polyethylene terephthalate substrate with bending deformation. The changes in the magnetic properties of the Pt/Co/Pt film with deformation were analyzed using magneto-optical Kerr-effect microscopy. The film was bent in one direction using cylindrical rods or semicylindrical grooves of different radii and then restored to the initial flat state. No significant changes in the magnetic properties due to bending strain were observed below a critical bending curvature. However, for bending curvatures above +0.25 mm−1 or below −0.14 mm−1, the magnetic domain shape changed from circular to elongated ellipses, perpendicular to the bending direction, and the coercivity of the film increased by 10%–30%. Furthermore, the domain wall motion exhibited a distinct anisotropic behavior, with ∼12-fold difference in the velocity of domain wall motion in different directions. Conclusively, the magnetic properties of the Pt/Co/Pt film fabricated on a flexible substrate exhibited irreversible changes beyond a critical deformation of +2.44% or −1.37%.

Dzyaloshinskii-Moriya interaction and magnetic anisotropy in Pt/Co/Au trilayers modified by Ga+ ion irradiation

The influence of 30 keV Ga+ ion irradiation in the fluence range 0 ÷ 1·1016 ions/cm2 on magnetic properties of Pt(bottom)/Co(3 nm)/Au(top) trilayers grown by the molecular beam epitaxy was studied. Polar magnetooptical Kerr effect magnetometry and Brillouin light scattering spectrometry were used to measure the magnetic anisotropy and the strength of Dzyaloshinskii-Moriya interaction (DMI). The as-deposited sample exhibits in-plane magnetization with an effective anisotropy field of −0.35 ± 0.02 T. Magnetic anisotropy gradually grows as the ion fluence is increased and out-of-plane magnetic anisotropy appears for the fluence above ∼ 3·1015 ions/cm2. The frequency asymmetry in Stokes and anti-Stokes lines Δf, being a measure of DMI strength, was determined from Brillouin light scattering investigations as a function of applied fluence. The effective DMI constant is equal to −0.48 ± 0.05 mJ/m2 in the as-deposited sample. While increasing fluence the parameter Δf: (i) varies non-monotonically (with two maxima) for F smaller than F≈1015 ions/cm2 and (ii) gradually decreases to zero for higher fluences. Our results can be used for the adjustment of DMI interaction in the manufacturing of magnonic nano-devices.

Enhanced flux pinning of single grain bulk (Gd, Dy)BCO superconductors processed by cold-top-seeded infiltration growth method

Single grain (Gd, Dy)BCO bulks were fabricated via cold-top-seeded infiltration growth process in air. Microstructural observations clarified that the size and dispersion of embedded (Gd, Dy)2BaCuO5 (211) secondary phase particles strongly varied in dependence of the grain refiners. The combined addition of Pt and CeO2 in each amount of 0.2 wt% increased the critical current density (Jcab, B‖c-axis) to 105 A/cm2 at 77 K and self-field. The microstructural and magnetic properties of Pt and CeO2 doped sample exhibited high homogeneity throughout the bulk sample. The optimum amount of Dy-211 is added to GdBCO along with Pt and CeO2 resulted in highest superconducting Jcab of 72 kA/cm2 at an applied magnetic field of 2.2 T with improved flux pinning which is confirmed by high values of the reduced fields (hmax = Ha/Hirr).

Study on the Gilbert damping of polycrystalline YIG films with different capping layers

This paper describes the effect of 5-nm thick platinum (Pt), aluminum (Al) and silicon oxide (SiOx) capping layers on the static and dynamic magnetic properties of 400-nm thick polycrystalline YIG films deposited on a Pt buffer layer. Both static and dynamic magnetic properties of Pt capped YIG film are totally different among all YIG films. Namely, the squareness of the magnetization curve for Pt capped YIG film increases, indicating that Pt capped YIG film is magnetically softer than other YIG films. Interestingly, the effective Gilbert damping parameter of Pt capped YIG films is about four times as large as those of other YIG films, and its value is approximately 9.52 × 10−4. However, the value of Gilbert damping is 2.55 × 10−4, 3.46 × 10−4 and 3.85 × 10−4 respectively for no capping, SiOx capping and Al capping samples respectively. This huge change in Gilbert damping parameter is mainly originating from the spin pumping effect, which arises at the interface of a material having strong spin orbit interaction such as Pt. Moreover, the enourmous increase in the value of effective anisotropic field and decrese in effective saturation magnetization indicates interface anisotropy is induced in Pt capped sample. These results suggest that the static and dynamic magnetic properties of YIG film can be controlled by selecting an appropriate capping layer.

Half-metallicity versus symmetry in half-Heusler alloys based on Pt, Ni, and Co: An ab initio study

Using first principles calculations based on density functional theory, we study the geometric, electronic, and magnetic properties of Pt, Ni and Co-based half Heusler alloys, namely, Pt$BC$, Ni$BC$ and Co$BC$ ($B$ = Cr, Mn and Fe; $C$ = Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te). We calculate the formation energy of these alloys in various crystal symmetries, which include, the (face-centered) cubic $C1_{b}$ ($F\bar{4}$3m), orthorhombic ($Pnma$), as well as hexagonal ($P\bar{6}2m$ and $P6_{3}/mmc$) structures. It has been observed that out of all the 108 structures, studied here, energetically stable cubic structure is observed for only 18 materials. These alloys are primarily having either a $C$ atom or an $A$ atom with a high atomic number. We also observe that along with the alloys with $C$ atoms from group IIIA, IVA and VA -- alloys with $C$ atoms from group VIA are also found to be, by and large, energetically stable. To examine the relative stabilities of different symmetries in order to search for the respective lowest energy state for each of the above-mentioned systems, as well as to find whether a material in the ground state is half-metallic or not, we analyze the formation energy, and the electronic density of states, in detail. Based on these analyses, the possibility of existence of any {\it one-to-one relationship} between the {\it cubic symmetry} and the {\it half-metallicity} in these half Heusler alloys is probed. Subsequently, we predict about the existence of a few new {\it non-cubic} half Heusler alloys with substantially low density of states at one of the spin channels and reasonably {\it high spin polarization at the Fermi level}

Electronic and Magnetic Properties of Pt Based Intermetalic LaPtAs and LaPt2As Compounds

We report the synthesis of polycrystalline LaPtAs and LaPt2As via solid state reactions and their temperature dependent magnetic and electrical transport properties. Crystal structures of both samples are suggested to be orthorhombic with a Pmmm space group. Temperature and field dependent magnetization measurements show that the splitting of field cooling and zero field cooling curves (initiation of irreversibility) take place at temperatures just below the Curie temperatures for both samples. This behavior is a characteristic of magnetic nanoparticles. Therefore, we propose that the magnetization arises from nanosized platinum clusters due to partial filling of the available interstitial sites. Temperature (T) dependent resistivity measurements of both alloys show metallic behavior at high temperatures and resistivity curve bends away from classical linear T dependence toward the temperature axis in the intermediate temperature range. This behavior is attributed to phonon induced interband s–d scattering. The main contribution to the resistivity at low temperatures is suggested to arise from the scattering of conduction electrons by spin-waves, in the presence of strong spin–orbit coupling due to Pt atoms. We discuss the role of spin–orbit effect on the electronic structure and the magnetic state of both samples based on various nano-scale structures.

Global Geometry Optimization and magnetic properties of Pt and FePt Clusters

Abstract The ground state geometry and the electronic and magnetic structure of small FePtn, n = 3,4,5 and 6, clusters are reported. The optimization of the geometry is carried out by means of graph theory, and the electronic energy is calculated selfconsitently within the ab initio density functional theory that includes spin-orbit coupling. In particular we present in detail the geometry optimization procedure and present, as particular examples, the evolution of those properties as a function of the cluster size.

Magnetic interactions and electronic structure of $$\hbox {Pt}_{2}\hbox {Mn}_{1-x}\hbox {Y}_{x} \hbox {Ga (Y = Cr and Fe)}$$ Pt 2 Mn 1 - x Y x Ga (Y = Cr and Fe) system: An ab-initio calculation

First principles density functional theory based calculations have been carried out to predict the effects of Mn replacement by Fe and Cr on electronic as well as magnetic properties of Pt$_{2}$MnGa as well as Ni$_{2}$MnGa. All the materials studied here are predicted to have conventional Heusler alloy structure in their ground state and they are found to be electronically stable on the basis of their respective formation energy. The replacement of Mn by Fe leads to a ferromagnetic ground state whereas in case of Mn replacement by Cr an {\it intra-sublattice} anti-ferromagnetic configuration has been observed to have lower energy. We study the magnetic exchange interaction between the atoms for the materials with ferromagnetic and anti-ferromagnetic configurations to show the effects of Fe and Cr substitution at Mn site on the magnetic interactions of these systems. Detailed analysis of electronic structure in terms of density of states has been carried out to study the effect of substitution.

ChemInform Abstract: Magnetic Properties of Pt‐Based Nanoalloys: A Critical Review

AbstractReview: 156 refs.

Magnetic Properties of Pt-Based Nanoalloys: A Critical Review

In recent years, magnetic nanoalloys (MNAs) have attracted many attentions from all over the world, due to their potential applications in the broad fields of magneto-optics, data storage, engineering, and biology. Among these MNAs, Pt–M (M = Fe, Co, Ni) MNAs have been considered to be the most promising ones, due to their superparamagnetism and response to a magnetic field. Here, we firstly review the experimental work on the synthesis, characterization, and magnetic properties of Pt–Fe, Pt–Co, and Pt–Ni MNAs. Then, we discuss the recent theoretical work on Pt–Fe, Pt–Co, and Pt–Ni MNAs. Moreover, we also review the main applications of Pt–Fe, Pt–Co, and Pt–Ni MNAs in the fields of biology, information storage, and magnetic separation. It is found that the size, shape, and composition of Pt–Fe, Pt–Co, and Pt–Ni MNAs play a critical role on their fundamental magnetic properties from both the experimental and theoretical points of view. It is expected that this review could be a valuable resource for both experimental and theoretical researchers, who are interested in Pt-based MNAs.

Atomic under-coordination fascinated catalytic and magnetic behavior of Pt and Rh nanoclusters.

Density functional theory (DFT) calculations with local spin density discrimination have been performed to examine the effect of atomic under-coordination on the catalytic and magnetic properties of cuboctahedral (CO) and marks decahedral (MD) structured Pt and Rh nanoclusters. Consistency between theoretical calculations and experimental observations confirmed the predictions based on the framework of bond-order-length-strength (BOLS) correlation and nonbonding electron polarization (NEP) notations. The BOLS-NEP notation suggests that the shorter-and-stronger bonds between under-coordinated atoms induce local densification and quantum entrapment of core electrons, which then polarize the otherwise conducting electrons and result in shifts of the binding energy. Such strong localization resolves the intriguing catalytic and magnetic attributes of Pt and Rh nanoclusters.

First-principles investigations of the structural, electronic, and magnetic properties of Pt13−nNin clusters

Abstract First-principles method based on the density functional theory has been utilized to calculate the structural, electronic and magnetic properties of Pt 13− n Ni n ( n = 0–13) clusters. For Pt 13− n Ni n clusters, Ni atoms are mainly found in the cluster core and Pt atoms are segregated to the cluster surface. The calculated binding energies of Pt 13− n Ni n clusters decrease with increasing Ni concentration. Through the bader charge and difference charge density analyses, it is observed that the small charge transfer is from Ni to Pt. In the total and partial density of states of Pt 13− n Ni n clusters, Pt 5d and Ni 3d orbitals make the main contribution to the electronic states and play an important role in determining the magnetism of Pt 13− n Ni n clusters. From n ⩾ 2, the calculated magnetic moments of Pt 13− n Ni n clusters increase to the maximum (8.34 μ B ) in Pt 2 Ni 11 cluster as a function of Ni concentration and then decrease slightly. The variation in the magnetic behavior of Pt 13− n Ni n clusters can be attributed to the exchange splitting of the energy bands near the Fermi level.

Synthesis and magnetic properties of hybrid nanostructures of Pt–FexOy

We report the synthesis conditions and magnetic properties of Pt and iron oxide (Pt–FexOy) hybrid nanostructures. The injection time and temperature of the Fe precursor after the decomposition of the Pt precursor are found to be the key parameters for the tuning of FePt to Pt–FexOy nanoparticles. The particle shape can be controlled from spherical to cubic by selective molar ratios of surfactants and solvents. A comparative study of the dynamic and static magnetic properties of Pt–FexOy and FexOy, (after etching of Pt) is presented. The effective anisotropy of Pt–FexOy is found to be one order of magnitude higher than that of etched FexOy. Consequently, a strong enhancement of the blocking temperature is observed which is attributed to the enhanced interfacial anisotropy between Pt and FexOy layers.

Pt3 and Pt4 clusters on graphene monolayers supported on a Ni(111) substrate: Relativistic density-functional calculations

Density-functional theory including spin-orbit coupling and corrections for dispersion forces has been used to investigate the structural and magnetic properties of Pt(3) and Pt(4) clusters deposited on a graphene layer supported on a Ni(111) substrate. It is shown that the strong interaction of the Pt atoms with the Ni-supported graphene stabilizes a flat triangular and a slightly bent rhombic structure of the clusters. Pt atoms are located nearly on top of the C atoms of the graphene layer, slightly shifted towards the bridge positions because the Pt-Pt distances are larger than the C-C distances of the graphene sheet lattice-matched to the Ni support. The strong interaction with the substrate leads to a substantial reduction of both the spin and orbital moments of the Pt atoms, not only compared to the clusters in the gas-phase, but also compared to those adsorbed on a freestanding graphene layer. The trends in the magnetic moments and in the magnetic anisotropy of the cluster/substrate complex have been analyzed and it is demonstrated that the anisotropy is dominated by the Ni support.

Structural and magnetic properties of Pt in Co/Pt multilayers

[Co(30 Å)/Pt( x Å)] 20 multilayers with the Pt layer thicknesses varying from 5 Å to 20 Å were characterized structurally by high angle X-ray diffraction, X-ray reflectivity, X-ray absorption spectroscopy and magnetically by X-ray magnetic circular dichroism. It is found that the structure and magnetic properties of Pt have a strong correlation with the Pt layer thickness. The 20 Å thickness Pt layer is not almost influenced by the adjacent Co layer and the nearest neighbors are dominated by Pt–Pt shells. With decreasing Pt layer thickness, the nearest neighbors are gradually dominated by Pt–Co shells and the Pt–Co intermixing regions also remarkable increase at the interfaces, especially for the 5 Å thickness Pt layer. The orbital and spin magnetic moments as well as the ratio m orb / m spin all decrease systematically with increasing Pt layer thickness, indicating that the interface atoms are polarized by direct Pt–Co hybridization, but that the adjacent layers are polarized by Pt–Pt interactions.

Magnetic properties of Pt–Ir nanowires

We study the magnetic properties of Pt 1− x Ir x nanowires by using the ab-initio wien2k code, being 0 ⩽ x ⩽ 1. It has been established in the literature that Pt and Ir nanowires show very different behaviors if spin–orbit coupling (SOC) is considered or not in the calculation of their electronic structure. Pt nanowires have magnetic order only if SOC is considered, but Ir ones show the opposite behavior. In the case of Pt 1− x Ir x nanowires and without considering SOC, the spin magnetic moment as a function of the Ir concentration ( μ vs. x) shows an almost linear behavior between the spin magnetic moments of pure wires. While μ Ir is relatively high, the μ Pt presents very low values. On the contrary, if SOC is taken into account, a very interesting behavior is found. While the pure wires have low average magnetic moment values, being zero for Ir one and 0.15 μ B for the Pt one, the curve μ vs. x shows a maximum at x = 1/2 of about 0.75 μ B. We discuss the influence of equilibrium bond length and hybridization effects on the electronic properties of Pt 1− x Ir x nanowires.

Modulation-induced effects in PtNi multilayers enhanced magnetization, perpendicular anisotropy and its instability

Magnetic properties of Pt m Ni n multilayers, grown by vapor deposition on Kapton, Si or glass, have been studied as function of the layer thickness m and n (1–10, in atomic planes). Magnetization enhancement (by up to 15% over that of pure Ni) and perpendicular anisotropy (for n about two atomic planes) were observed. The latter presented an instability with temperature, indicative of thermally-assisted domain effects.

Effect of heavy rare earths on the catalytic and magnetic properties of platinum re-forming catalysts

The magnetic properties of Pt—RE (RE  Gd, Tb, Dy, Ho, Tm) catalysts supported on γ-Al 2O 3 were studied using a Faraday magnetic balance. The conversion of cyclohexane, n-hexane and n-heptane on these catalysts has been investigated using a pulsed catalytic flow microreactor. The results show that heavy rare earths can improve the activity, stability and magnetic properties of platinum re-forming catalysts. The relationship between the adsorption and magnetic susceptibility of Pt—Gd/γ-Al 2O 3 catalysts was also investigated under different conditions.

Magnetic properties of Co/Pt-multilayers

The magnetic properties of (111)-textured Co/Pt-multilayers have been studied theoretically by means of spin-polarized LMTO-band-structure calculations. In contrast to the interpretation of earlier experimental investigations, the Pt-layers have been found to be significantly magnetized by the adjacent Co-layers. This finding ensures that the Co-layers are exchange-coupled even for relatively thick Pt-interlayers. To get some information on the consequences of interface mixing we have used the ASA-version of the spin-polarized relativistic KKR-method of band-structure calculation to investigate the electronic and magnetic properties of Pt-(Co)-impurities in the various layers of the Co/Pt-multilayers. Our non-self-consistent results indicate that for most cases a slight increase in the magnetic moments has to be expected. To study experimentally the magnetic properties of the Pt-layers of vapor-deposited samples we have made use of the magnetic dichroism in X-ray absorption. This new technique allows to probe the Pt-layers separately and to estimate the average moment of this subsystem. While the estimated moments are in all cases somewhat higher than our corresponding theoretical results, their dependence on the Pt-layer thickness is in very satisfying agreement with the theoretical predictions.

Effect of Transition Metal Solutes on Magnetic Properties of Pt

Magnetic susceptibility and NMR measurements on Pt with addition of 3d, 4d and 5d transition metal solutes were carried out at helium temperature to study the effect of nonmagnetic and magnetic solutes on the magnetic properties of Pt. The change of the host d band susceptibility and its valence number dependence were obtained and compared with the theory by Asano et al . for nonmagnetic solute alloy. From this comparison, it was concluded that the change of the host d band susceptibility arises from the change of the density of states at E F of Pt. As for magnetic alloys, it was found that the effect due to the polarization of conduction electrons by the localized magnetic moment of solute is predominant in the alloys with low T K ( Pt Co, Pt Fe), whereas in the alloy with high T K ( Pt Cr), the same mechanism as that of nonmagnetic alloy becomes important.