Correlations between magnetic transition temperatures and the average weighted valence band electron concentration ((s + d) electrons/atom) have led to the development of a phenomenological model that predicts the influence of elemental substitution on the magnetostructural response of bulk B2-ordered Fe(Rh_1−xM_x) or (Fe_1−xM_x)Rh alloys (M = transition elements; x < 6 at. %). Validation of this model is provided through synthesis and characterization of FeRh with Cu and Au additions. The data and associated trends indicate that the lattice and electronic free energies are both equally important in driving the magnetostructural transition in the bulk FeRh system.

Linear magnetoresistance (LMR) occurs in semiconductors as a consequence of strong electrical disorder and is characterized by nonsaturating magnetoresistance that is proportional to the applied magnetic field. By investigating a disordered MnAs-GaAs composite material, it is found that the magnitude of the LMR is numerically equal to the carrier mobility over a wide range and is independent of carrier density. This behavior is complementary to the Hall effect that is independent of the mobility and dependent on the carrier density. Moreover, the LMR appears to be insensitive to the details of the disorder and points to a universal explanation of classical LMR that can be applied to other material systems.

In this work, we demonstrate that the magnetocaloric response of FeRh-based compounds may be tailored for potential magnetic refrigeration applications by chemical modification of the FeRh lattice. Alloys of composition Fe(Rh_1−xA_x) or (Fe_1−xB_x)Rh (A = Cu, Pd; B = Ni; 0 < x < 0.06) were synthesized via arc-melting and subsequent annealing in vacuum at 1000 °C for 48 h. The magnetocaloric properties of the FeRh-based systems were determined using isothermal M(H) curves measured in the vicinity of the magnetostructural temperature (T_t). It is found that the FeRh working temperature range (δT_FWHM) may be chemically tuned over a wide temperature range, 100 K ≤ T ≤ 400 K. While elemental substitution consistently decreases the magnetic entropy change (ΔS_mag) of the FeRh-based ternary alloys from that of the parent FeRh compound (ΔS_mag,_FeRh ∼ 17 J/kg K; ΔS_{mag,FeRh-ternary =} 7–14 J/kg K at H_app = 2 T), the net refrigeration capacity (RC), defined as the amount of heat that can be transferred during one magnetic refrigeration cycle, of the modified systems is significantly higher (RC_FeRh ∼ 150 J/kg; RC_{FeRh-ternary =} 170–210 J/kg at H_app = 2 T). These results are attributed to stoichiometry-induced changes in the FeRh electronic band structure and beneficial broadening of the magnetostructural transition due to local chemical disorder.