Influence of composition on the structure, electric and magnetic properties of Pd-Mn-P and Pd-Co-P amorphous alloys

Materials Science, composition on the structure, electric and magnetic, properties of Pd-Mn-P, Pd-Co-P amorphous alloys

Marzwell, Neville Ingersoll ; Duwez, Pol E.

University:California Institute of Technology

Department:Engineering and Applied Science

关键词: Materials Science, composition on the structure, electric and magnetic, properties of Pd-Mn-P, Pd-Co-P amorphous alloys;   

Others  :  https://thesis.library.caltech.edu/8587/1/marzwell-ni-1973.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The influence of composition on the structure and on the electricand magnetic properties of amorphous Pd-Mn-P and Pd-Co-P preparedby rapid quenching techniques were investigated in terms of (1) the 3dband filling of the first transition metal group, (2) the phosphorusconcentration effect which acts as an electron donor and (3) the transition metal concentration.

The structure is essentially characterized by a set of polyhedrasubunits essentially inverse to the packing of hard spheres inreal space. Examination of computer generated distribution functionsusing Monte Carlo random statistical distribution of these polyhedraentities demonstrated tile reproducibility of the experimentally calculated atomic distribution function. As a result, several possible"structural parameters" are proposed such as: the number of nearestneighbors, the metal-to-metal distance, the degree of short-range orderand the affinity between metal-metal and metal-metalloid. It is shownthat the degree of disorder increases from Ni to Mn. Similar behavioris observed with increase in the phosphorus concentration.

The magnetic properties of Pd-Co-P alloys show that they areferromagnetic with a Curie temperature between 272 and 399°K as thecobalt concentration increases from 15 to 50 at.%. Below 20 at.% Co theshort-range exchange interactions which produce the ferromagnetism areunable to establish a long-range magnetic order and a peak in themagnetization shows up at the lowest temperature range . The electricresistivity measurements were performed from liquid helium temperaturesup to the vicinity of the melting point (900°K). The thermomagneticanalysis was carried out under an applied field of 6.0 kOe. Theelectrical resistivity of Pd-Co-P shows the coexistence of a Kondo-likeminimum with ferromagnetism. The minimum becomes less importantas the transition metal concentration increases and the coefficientsof ℓn T and T^2 become smaller and strongly temperature dependent.The negative magnetoresistivity is a strong indication of the existenceof localized moment.

The temperature coefficient of resistivity which is positivefor Pd- Fe-P, Pd-Ni-P, and Pd-Co-P becomes negative for Pd-Mn-P. It ispossible to account for the negative temperature dependence by thelocalized spin fluctuation model and the high density of states at theFermi energy which becomes maximum between Mn and Cr. The magnetizationcurves for Pd-Mn-P are typical of those resulting from the interplay of different exchange forces. The established relationship between susceptibility and resistivity confirms the localized spin fluctuation model. The magnetoresistivity of Pd-Mn-P could be interpretedin tenns of a short-range magnetic ordering that could arisefrom the Rudennan-Kittel type interactions.