The determination of collective spin excitations and their contribution to the intrinsic resistivity via spin-flip electronic scattering are addressed for $3d$ ferromagnets using magnetotransport experiments. We present longitudinal high-field magnetoresistance (MR) measurements from 4 to 500 K and up to 40 T on Fe-, Co-, and Ni-patterned thin films. Well above the technical saturation of the magnetization\char22{}i.e., in the paraprocess regime\char22{}we report an almost linear and nonsaturating negative MR of around 0.01\char21{}0.03 \ensuremath{\mu}\ensuremath{\Omega} cm ${\mathrm{T}}^{\mathrm{\ensuremath{-}}1}$ at 300 K for the three magnets. We demonstrate its magnetic origin, and we assign this high-field resistivity decrease to the electron-magnon scattering and the spin-wave damping in high fields. We propose a theoretical calculation of the magnetic resistivity originating from spin-flip intraband $s\ensuremath{-}s$ and $d\ensuremath{-}d$ and interband $s\ensuremath{-}d$ transitions via electron-magnon diffusion including both the high-field effect on the magnon spectrum and the magnon mass renormalization. Convincing agreements between the high-field measurements and our model provide a unique estimate of the pure magnetic resistivity in $3d$ ferromagnets. Our analysis also gives an insight into the low-energy spin waves\char22{}i.e., the theoretical magnon saturation field and the magnon mass renormalization consistent with neutron scattering results for the three magnets.

Electron-magnon scattering and magnetic resistivity in 3d ferromagnets

Systematic study of anisotropic transport and magnetic properties of RAgSb2 (R=Y, La–Nd, Sm, Gd–Tm)

Transport and magnetic properties are reported for ternary skutterudites ${\mathrm{La}}_{0.83}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}.$ Physical properties of ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ are dominated by crystal electric field effects, yielding in the magnetic triplet ${\ensuremath{\Gamma}}_{5}$ as ground state. As a result, long-range magnetic order appears below 4.6 K. ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ exhibits an unusually high electronic contribution to the specific heat ${C}_{p}/T$ of several hundred ${\mathrm{m}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{}\mathrm{K}}^{2},$ and a significant value of a nuclear Schottky contribution is derived below about 1 K, primarily related to ${}^{141}\mathrm{Pr}$ with a nuclear spin $I=5/2.$ The figure of merit at room temperature, expressing the thermoelectric performance of ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12},$ is about 0.075.

Crystal field effects and thermoelectric properties of PrFe 4 Sb 12 skutterudite

The electrical resistivity of antiferromagnetic metals is discussed on the basis of the two band model. The general expression in terms of the dynamical susceptibility is obtained. The resistivity is studied by using the self-consistent renormalization theory of spin fluctuations. The resistivity at low temperatures is proportional to T 2 and its coefficient diverges as |α-1| -1/2 as one approaches the critical boundary of antiferromagnetism. It is pointed out that in the ordered phase the effect of the gap in the conduction band is important. Especially, this effect plays a crucial role in the temperature dependence of the contribution of the spin waves. It is proportional to T 5 and T 2 at the temperatures lower and higher, respectively, than the gap energy. At high temperatures the resistivity is significantly suppressed from that calculated by using RPA results for the spin fluctuations and can have a tendency towards saturation.

Electrical Resistivity of Antiferromagnetic Metals

Effect of magnetic field on spin fluctuations in weakly ferromagnetic metals

A simple expression for the magnetoresistance of the antiferromagnetic metals due to the electron-spin scattering by the s - d interaction is obtained using the molecular field approximation for the spin system The expression includes the ferromagnetic case It is shown that in the antiferromagnetic case the positive magnetoresistance appears below the transition point, in contrast to the negative-magnetoresistance in the case of the para or ferromagnetic case In the ferromagnetic case the negative magnetoresistance shows a deep and finite valley at the transition point, which is consistant with the experiments of the ferromagnetic rare-earth metals such as Gd and Tb

Magnetoresistance of Antiferromagnetic Metals Due to s-d Interaction

Magnetoresistance due to Electron-Spin Scattering in Antiferromagnetic Metals at Low Temperatures

/pdf/negative-magnetoresistance-of-ferromagnetic-metals-due-to-4m5vcvyqes.pdf

Negative Magnetoresistance of Ferromagnetic Metals due to Spin Fluctuations

The electrical resistivity of antiferromagnetic metals due to electron-magnon scattering is calculated on the sf model in the low temperature region . by the use of the variational approach to the Boltzmann equation. The re~istivity p varies with temperature T as P"' T' for TN~T~D (TN: Neel temperature, D: anisotropy energy of the spin system) and as p "'Texp(- VTND/T) for TN, D~T: The effects of the Umklapp scattering and the inter­ band scattering to the total conductivity are shown to be small compared with that due to the intraband scattering. The nature of the approximation in the calculation of the resistivity which .was used in a previous paper is discussed and corrected.

/pdf/on-the-electrical-resistivity-of-antiferromagnetic-metals-at-410z61nykq.pdf

Hiroshi Yamada

Papers

Magnetoresistance of Antiferromagnetic Metals Due to s-d Interaction

Magnetoresistance due to Electron-Spin Scattering in Antiferromagnetic Metals at Low Temperatures

Negative Magnetoresistance of Ferromagnetic Metals due to Spin Fluctuations

On the Electrical Resistivity of Antiferromagnetic Metals at Low Temperatures