The crystal and magnetic structure of tetragonal Pd3Mn

Journal of Physics-condensed Matter, 2012

In this paper we shall study three binary alloy systems, one constituent of which is Mn. The other constituents are chosen from a particular column of the periodic table: Ni(3d), Pt (4d) and Pd (5d). As we go down the column, the d-bands become wider, discouraging spin-polarization. In a disordered alloy, the situation becomes more complicated, as the exchange interaction between two atoms is environment dependent. We shall compare and contrast their magnetic behaviour using robust electronic structure techniques. In all three alloy systems conjectures are made to explain experimental data. In this paper we shall examine whether there is any basis to these conjectures.

Journal of Alloys and Compounds, 2004

The present work shows results on the surface effects produced by electrolytic hydrogenation and desorption of Ni-Pd alloys (60Ni-40Pd and 40Ni-60Pd, wt.%). The behaviour of these two alloys is rather similar to that of pure nickel rather than pure palladium. Intergranular and transgranular cracks were observed just after the electrolytic charging. During the natural aging the cracks become larger and propagate, as observed by scanning electron microscopy. The hydride phases formed are very unstable at room temperature and normal pressure. X-ray diffractograms were used to obtain a microstrain and microstress analysis of the NiPd solid solution and hydride phases. Magnetization curves of the Ni60-40Pd show that trapped hydrogen atoms remain in the NiPd phase after hydride decomposition and decrease the magnetization saturation and the magnetic permeability.

Journal of Alloys and Compounds, 2012

Powder samples of GdMn 2 H x hydrides, with 0pxp4.3, have been characterized by X-ray analysis and SQUID magnetometry for temperatures ranging between 4 and 375 K. The observed phase transformations as a function of temperature and hydrogen concentration are discussed and explained. The correlated changes of magnetization and susceptibility have been analyzed and the temperature dependent development of magnetic ordering of Mn and Gd atoms as a function of temperature and hydrogen content has been discussed. The structural and magnetic phase diagrams have been proposed. r

Processes, 2020

Martensitic transition and magnetic response of Ni50−x Pdx,y Mn36 Sn14−y (x = 0, 1, 2 and y = 0, 1) Heusler alloys were analysed. The crystalline structure of each composition was solved by X-ray diffraction pattern fitting. For x = 1 and 2, the L21 austenite structure is formed and, for y = 1, the crystallographic phase is a modulated martensitic structure. From differential scanning calorimetry scans, we determine characteristic transformation temperatures and the entropy/enthalpy changes. The temperatures of the structural transformation increase with the addition of Pd to replace Ni or Sn, whereas the austenitic Curie temperature remains almost unvarying. In addition, the magneto-structural transition, investigated by magnetic measurements, is adjusted by suitable Pd doping in the alloys. The peak value of the magnetic entropy changes reached 4.5 J/(kg K) for Ni50Mn36Sn13Pd1 (external field: 50 kOe).

Journal of Alloys and Compounds

A study of the kinetics of hydrogen-induced ordering from "as-quenched" and initially ordered (L12~-type) states in Pd3Mn to the L12-type structure has been carried out to examine the conditions necessary for the ordering, i.e. the hydrogen pressures, temperatures and times and to consider the ordering mechanism, using electrical resistance measurements. The ordering rate for the initially ordered alloy of the L12~,-type structure is slower than that for the initially "as-quenched" state. The hydrogen-induced ordering to the L12-type structure may occur from the periodic one-dimensional antiphase domain structure of the L12~, type with a cubic fundamental cell, in which a step shift, (a2+a3)/ 2, is introduced at every two cells along the al axis, by attaining a particular stress state due to the lattice expansion caused by the preferential occupation of hydrogen in the octahedral sites of six palladium nearest-neighbor atoms.

Journal of Physics: Condensed Matter, 2009

Magnetic, magnetocaloric and magnetoresistance properties of the intermetallic compound Nd 7 Pd 3 have been investigated. It exhibits a first-order magnetic phase transition at its ferromagnetic ordering temperature (T C = 34 K). Just above the T C , the magnetization isotherms exhibit a metamagnetic transition from the paramagnetic to a ferromagnetic state. In the immediate vicinity of T C , a field change of only 10 kOe leads to the giant magnetocaloric effect of 13 J mol −1 K −1 . For a field change of 50 kOe a large magnetoresistance of ∼21% is observed near T C . First-principles electronic structure calculations indicate that the first-order phase transition in Nd 7 Pd 3 may originate from the peculiar nature of the density of states near the Fermi level.

Physical Review B, 2002

The electronic and magnetic structure of Mn 3 Rh, including noncollinear structures, in the ordered and disordered states have been investigated by the tight-binding linear-muffin-tin orbital method. A magnetic long-range order of the triangular (T1) structure in the ordered state is reflected in a dip around the Fermi level in the density of states. This characteristic feature can be retained in the multiple-Q spin-density-wave ͑SDW͒ structures in the disordered alloy, implying that a stable antiferromagnetic order also remains in the disordered alloy. The most stable structure in the disordered alloy is suggested to be the 3Q-SDW structure. From the effective exchange constant, the Néel temperature in the disordered alloy is estimated to be about 680 K, close to the experimental value of about 700 K. Compared to the Néel temperature of pure ␥-Mn metal, such a high value is pertinent to the change in the electronic structure caused by the addition of Rh.

Applied Physics Letters, 2015

The effect of hydrogenation on a 14 nm Co 14 Pd 86 /Al 2 O 3 (0001) thin film was investigated on the basis of the magnetooptical Kerr effect. After exposure to H 2 gas, the squareness of the hysteresis loop showed a large transition from approximately 10% to 100% and the saturation Kerr signal was reduced to nearly 30% of the pristine value. The reversibility of the transition was verified and the response time was within 2-3 s. These observations indicate that the hydride formation transformed the short-range coupled and disordered magnetic state of the Co 14 Pd 86 film to a long-range-ordered ferromagnetic state and induced appreciable decrease in the magnetic moment. The enhanced long-range-ordering and the reduction of the magnetic moment were attributed to the change of electronic structure in Co 14 Pd 86 with hydrogen uptake. V

International Journal of Hydrogen Energy, 1994

The solution of hydrogen in palladium-rich substitutional alloys has been of continuing interest since the pioneering studies of Thomas Graham on palladium-silver alloys, in the nineteenth century. The various palladium alloys exhibit different characteristics of hydrogen absorption compared with palladium (1, 2). Graham demonstrated considerable prescience in selecting the palladium-silver alloy system for his investigation of hydrogen absorption by a palladium alloy, since this alloy has subsequently proven to be the alloy of most interest.

Journal of Magnetism and Magnetic Materials, 1995

Measurements of the magnetic susceptibility g as a function of tempemane were made on polycrystalline samph~s from the alloy systems Cdt_:Mn:Ga2Se +, Zut_~MnzGazSe + and Cdt_zMn:In2Te + which had been subject~ to v~rio~s hea~ treatments. The I/X versus T carves indicated lhae for the Zn-S¢ alloys, for all values of z, samples slowly cooled to temperature were anfiferromagaetie showing ideal Curie-Weiss behaviour, bet for samples quenched from 700°C Lhe I~haviour was a mixture of antiferromagnefic and spin-glass. For th¢ Cd-Se alioys, samples from the 14-2 m t'a~g¢ (0.6 < z < 1.13) showed very similar behaviour, but in the 14 range (0 < z < 0.6) even the very slow|y caoled samp~ showed a mixture of amifen'omagnetic and spin-glass hehaviour. For the Cd-Te alk~ys, all samples, however I,~e.a~-treiged.