Ferromagnet, spin polarization

Yamamoto, Y Miura, T Suzuki, M., Kawamura, N Miyagawa, H Nakamura, T Kobayashi, K Teranishi, T. and Hori, H. (2004) Direct observation of ferromagnetic spin polarization in gold nanopartides. Physical Review Letters, 93, 116801. 

In Chap. A, we have seen that, in the Stoner model, (ferromagnetic) spin-polarization of electrons originates two electron states E+ and E from each electron state E of a non-spin-polarized electron band, the difference between the two being (E+ - E ) = Im, where I is the Stoner parameter and m = n+ - n is the magnetization density. 

Direct observation of ferromagnetic spin polarization in gold nanoparticles, Y. Yamamoto, T. Miura,... 

Concluding this section, two interesting variants of the STM should be addressed. The spin-polarized STM (SPSTM), which works with a ferromagnetic tip, can be used to probe surface magnetism with high resolution [5.47, 5.48]. Other modifications of the STM involve electromagnetic radiation, whereby two basic concepts can... 

The muffin-tin potential around each atom in the unit cell has been calculated in the framework of the Local-Spin-Density-Approximation using the ASW method. The ASW method uses the atomic sphere approximation (ASA), i.e. for each atom a sphere radius is chosen such that the sum of the volumes of all the overlapping spheres equals the unit cell volume. The calculation yields the expected ferromagnetic coupling between Cr and Ni. From the self-consistent spin polarized DOS, partial and total magnetic moment per formula unit can be computed. The calculated total magnetic moment is 5.2 pg in agreement with the experimental value (5.3 0.1 e calculations presented here have been performed... 

It is relatively common for DFT calculations to not explicitly include electron spin, for the simple reason that this approximation makes calculations faster. In materials where spin effects may be important, however, it is crucial that spin is included. Fe, for example, is a metal that is well known for its magnetic properties. Figure 8.10 shows the energy of bulk Fe in the bcc crystal structure from calculations with no spin polarization and calculations with ferromagnetic spin ordering. The difference is striking electron spins lower the energy substantially and increase the predicted equilibrium lattice constant by 0.1 A. 

Monsma DJ, Parkin SSP (2000) Spin polarization of tunneling current from ferromagnet/ AI2O3 interfaces using copper-doped aluminum superconducting films. Appl Phys Lett 77 720-722... 

In the Stoner theory for magnetism, it is shown that magnetic ordering is possible in a band scheme, when spin-polarization is energetically favorable the full discussion (see Chap. A) for the simpler case of ferromagnetism leads to a simple criterion known as the Stoner criterion ... 

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