Preliminary Results of Band Calculation for the YCo 5 Compound. Centro de Investigacion en Materiales Avanzados, S.C. Chihuahua, Chih.

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1 Preliminary Results of Band Calculation for the YCo 5 Compound M.C. Grijalva and J. Matutes-Aquino Centro de Investigacion en Materiales Avanzados, S.C. Chihuahua, Chih., Mexico

2 Introduction We are interested in the understanding of the origen of the magnetism in YCo 5 compound from the point of view of quantum mechanical calculations. We are presenting now some preliminary calculations for the Density of State of this compound. One reason is be able to understand the interband transitions information obtained using Parallel Electron Loss Energy Spectra (PEEL) in Transmission Electron Microscopy. Another reason is to be able to predict the preassure dependence of the Density of State for YCo 5.

3 Introduction The Local Density Approximation (LDA) To make the Density Functional Theory practical it is necessary to use an approximation scheme to deal with the exchange interaction functional. This is the Local Density Approximation (LDA) where the homogeneous interacting electron gas serves to model the exchangecorrelation energy. Reference: Jürgen Kübler Theory of Itinerant Electron Magnetism Oxford Science Publications2

4 Introduction The Augmented Spherical Wave Method The Augmented Spherical Wave Method (ASW Method) was developed by William (1979) using the Andresen s Linear Muffin-Tin Orbital Technique (LMTO technique). Reference: Jürgen Kübler Theory of Itinerant Electron Magnetism Oxford Science Publications 2

5 Introduction We use a computer program made by Proffesor Jürgen Kübler from the Institute of Solid State Physics, Darmstat University of Technology. The program is based on the Augmented Spherical Wave Method. This computer program allows the calculation of the spin up and spin down Density of States (DOS), the spin up and spin down Band Energy Structure (BES) and the degree of magnetic moment localization in different atoms within the unit cell of the crystal. This program do not includes the spin-orbit interaction. So we can not make any conclusion about magnetocrystalline anisotropy.

6 Density of States of Co and Y at K hcp structure hcp structure DOS (Number of states/unitcell.spin.ev) c/a= Co hcp µ Co = µ B µ Y = µ B DOS (Number of states/unitcell.spin.ev) c/a= Y hcp

7 Band Energy Structure for Co and Y at K Co hcp spin up-down Y hcp spin up-down k-points (numbered) k-points (numbered)

8 Density of States of YCo 5 at K DOS (Number of states/unitcell.spin.ev) YCo 5 µ Y = µ B µ I Co = µ B µ II Co = µ B Hexagonal c/a=

9 Band Energy Structure for YCo 5 at K YCo 5 spin up YCo 5 spin down k-points (numbered) k-points (numbered)

10 Density of States of YCo 5 hcp µ Y = µ B µ I Co = µ B µ II Co = µ B DOS (Number of states/unitcell.spin.ev) YCo 5 δ=-.5 DOS (Number of states/unitcell.spin.ev) YCo δ= DOS (Number of states/unitcell.spin.ev) µ Y = µ B µ I Co = µ B µ II Co = µ B YCo 5 δ= µ Y =. µ B µ I Co =. µ B µ II Co =. µ B

11 Conclusions Y is not magnetic Co is ferromagnetic YCo 5 is ferromagnetic. Both Y and Co have localized magnetic moments The YCo 5 at normal preassure (δ=) is ferro The YCo 5 at low preassure (δ=-.5) is ferro The YCo 5 at high preassure (δ=+.5) becomes para It will be of interest to make calculation at T>K using Statistic Thermodynamics Can we test the results with a Press Cell for δ>? Can we test the results with H 2 experiments δ<?

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