The anisotropic magnetoresistance effect in 3d transition metals and alloys is reviewed. This effect, found in ferromagnets, depends on the orientation of the magnetization with respect to the electric current direction in the material. At room temperature, the anisotropic resistance in alloys of Ni-Fe and Ni-Co can be greater than 5%. The theoretical basis takes into account spin orbit coupling and d band splitting. Other properties such as permeability, magnetostriction, and Hall voltage have no simple relationship to magnetoresistance. Anisotropic magnetoresistance has an important use as a magnetic field detector for digital recording and magnetic bubbles. Such detectors because of their small size are fabricated using thin film technology. Film studies show that thickness, grain size, and deposition parameters play a significant role in determining the percentage change in magnetoresistance. In general, the change is smaller in films than bulk materials. Several tables and graphs that list bulk and film data are presented.

Anisotropic magnetoresistance in ferromagnetic 3d alloys

Spontaneous resistivity anisotropy in Ni alloys

: This technical report reviews the available experimental data and information on the electrical resistivity and thermal conductivity of nine selected AISI stainless steels and presents the recommended values from near absolute zero (1 K) to above the melting point of the stainless steels (into the molten state). The nine selected stainless steels are AISI 303, 304, 304L, 316, 317, 321, 347, 410, and 430. The recommended values are generated as a result of critical evaluation, analysis, and synthesis of the available data and information. Data are synthesized.

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Electrical Resistivity and Thermal Conductivity of Nine Selected AISI stainless Steels

Publisher Summary This chapter discusses the transport properties of ferromagnets. The focus is on transport properties of the transition ferromagnets Fe, Co, and Ni and their alloys. In pure ferromagnetic metals, the “internal magnetoresistance” enhances the resistivity that is no longer proportional to the concentration of impurities. This effect is particularly important for Fe and a high transverse magnetoresistance. For demagnetized Fe polycrystals, it was pointed out that the apparent residual resistivity ratio would never increase beyond about 300, however pure the sample. It is now standard practice to measure the low temperature resistivity of Fe samples in a saturating longitudinal magnetic field to eliminate transverse magnetoresistance. This can reduce the apparent resistivity by a factor of five or more. In principle, a correction should still be made for the longitudinal magnetoresistance. In Ni samples, the enhancement of the residual resistivity by the internal magnetoresistance is less important than in Fe but still significant. For non-magnetic alloys, the low temperature magnetoresistance behavior generally follows Kohler's rule. Schwerer and Silcox showed by a careful study of dilute Ni alloy samples that for a given series of alloys the ordinary magnetoresistance follows a Kohler's rule, but that the Kohler function varied considerably with the type of scatterer.

Chapter 9 Transport properties of ferromagnets

Scattering mechanisms of conduction electrons in transition metals at low temperatures

The electrical resistivities of iron-base alloys with Cr, W, Mn, Ru, Co, Ni, Si, or Ge solutes, and of nickel-base alloys with Cr, Fe, Cu, or Pd solutes were measured from 4.2 \ifmmode^\circ\else\textdegree\fi{}K to above the Curie temperatures $\ensuremath{\theta}$. The solute resistivities ${\ensuremath{\rho}}_{r}(T)[={\ensuremath{\rho}}_{\mathrm{alloy}}(T)\ensuremath{-}{\ensuremath{\rho}}_{\mathrm{host}}(T)]$ were found to be strongly temperature dependent. Above \ensuremath{\sim} 300 \ifmmode^\circ\else\textdegree\fi{}K, the temperature dependence of ${\ensuremath{\rho}}_{r}(T)$ reflects changes in the electronic structure or in the scattering processes associated with the solutes and is related to changes in the magnetic order. The solute resistivities above 300 \ifmmode^\circ\else\textdegree\fi{}K were found to be in reasonable agreement with a spin-disorder model which explicitly involves the moments localized at the solute sites. Agreement with the well-known Mott band model for ferromagnetic effects in transport properties was not as satisfactory. An essential feature of the analyses of the data involved comparing resistivities of alloy and host corresponding to the same degree of magnetic order. This was accomplished by assuming the ferromagnetic effects in the resistivity scaled as $\frac{T}{\ensuremath{\theta}}$. The experimental results support the validity of this assumption.

Spin-Disorder Scattering in Iron- and Nickel-Base Alloys

The magnetoresistance of many polycrystalline samples of nickel alloyed with small concentrations of iron, cobalt, manganese, chromium, and carbon has been measured. An analysis of the data gave the result that all those specimens in which the conduction-electron scattering was dominated by one particular scattering center were found to obey Kohler's rule. However, the details of the magnetoresistance were different in each case, with the exception of the iron, cobalt, and manganese impurities, which formed one group. In addition, the thermal-scattering magnetoresistance and that due to deformation were different again. These observations confirm previous conclusions concerning the validity of Kohler's rule. Extremely large magnetoresistance was found for the iron, cobalt, and manganese group of impurities as scattering centers, which apparently is much larger than observed in any other system. This can be correlated with other electronic properties of the impurities, such as the resistivity and magnetic moment per unit concentration. In particular, the high magnetoresistance appears associated with the presence of large local moments. The zero-field anisotropy in the resistance is also correlated with these same properties. In spite of this correlation, we have no clear interpretation of the extreme magnetoresistance.

F. C. Schwerer

Papers

Spin-Disorder Scattering in Iron- and Nickel-Base Alloys

Scattering-Center Effects in the Magnetoresistance of Nickel