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Metallic magnetism and Invar M. Acet Experimentalphysik, Universität Duisburg-Essen.

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Presentation on theme: "Metallic magnetism and Invar M. Acet Experimentalphysik, Universität Duisburg-Essen."— Presentation transcript:

1 Metallic magnetism and Invar M. Acet Experimentalphysik, Universität Duisburg-Essen

2 - Structure of transition metals - Magnetism of transition metals - Magnetic instabilities and ‘Invar’ Outline

3 Band formation

4 Structure of the transition elements (elements with ‘wrong’ crystal structures) complex cubicbcchcp bccfcc

5 Allotropy in the 3d elements

6 The density of states and non-integral magnetic moment N   N   2.2  B  N  8 BCC Fe

7 Ferro and antiferromagnetic transition temperatures  -Mn

8 s+d electrons fcc Mn fcc Fe Rigid band model and the Slater-Pauling curve: Valence electron concentration dependence of the magnetic moment

9 Invar: Fe 65 Ni 35

10 Measuring the thermal expansion of the Eifel tower

11 Thermal expansion of solids ‘normal’ metals invar T (K)

12 Binding energy vs. atomic volume for a “normal” ferromagnet (schematic) Binding energy vs. atomic volume for “normal” and magnetically unstable ferromagnet (schematic) enhanced “negative” anharmonicity T (K)

13 What are instabilities at all?

14 Fe-Ni: Invar to Anti-invar

15 Summary of Magnetovolume Instabilities positive enhanced anharmonicity negative enhanced anharmonicity “anti-Invar” “Invar”

16 Moruzzi et al, PRB 39 (1989) Anti-invar in fcc-Fe and fcc-Mn

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18 Cu 2 MnAl Cu2MnSn Mn 3 SnC MnBi MnAl Ag 5 MnAl Mn 3 ZnC Au 4 Mn MnSb MnCrSb Pt 3 Mn Ni 3 Mn … Knowledge of magnetostructural properties vital for material design in - Spintronics - Magnetic shape memory - Nanomagnets Ferromagnetic Mn in a cubic environment

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