We report room temperature giant baroresistance (≈128%) in Fe49(Rh0.93Pd0.07)51. With the application of external pressure (P) and magnetic field (H), the temperature range of giant baroresistance (≈600% at 5 K, 19.9 kilobars and 8 T) and magnetoresistance (≈ −85% at 5 K and 8 T) can be tuned from 5 K to well above room temperature. It is shown that under external pressure, antiferromagnetic state is stabilized at room temperature and shows giant magnetoresistance (≈−55%). Due to coupled magnetic and lattice changes, the isothermal change in resistivity at room temperature under pressure (at constant H) as well as magnetic field (at constant P) can be scaled together to a single curve, when plotted as a function of X = T + 12.8 × H − 7.3 × P.

Room temperature giant baroresistance and magnetoresistance and its tunability in Pd doped FeRh

The first-order antiferromagnetic (AFM) to ferromagnetic (FM) transition in the functional material ${\text{Fe}}_{49}{({\text{Rh}}_{0.93}{\text{Pd}}_{0.07})}_{51}$ has been studied at low temperatures and high magnetic fields. We have addressed the nonmonotonic variation in lower critical field required for FM to AFM transition. It is shown that critically slow dynamics of the transition dominates below 50 K. At low temperature and high magnetic field, state of the system depends on the measurement history resulting in tunable coexistence of AFM and FM phases. By following cooling and heating in unequal magnetic field protocol it is shown that equilibrium state at 6 T magnetic field is AFM state. Glasslike FM state at 6 T (obtained after cooling in 8 T) shows reentrant transition with increasing temperature; viz., devitrification to AFM state followed by melting to FM state.

Low-temperature study of field-induced antiferromagnetic-ferromagnetic transition in Pd-doped Fe-Rh

A two-sublattice spin model is proposed with special four-spin interactions besides the usual exchange terms. The four-spin interaction terms are assumed not to be the even functions of the spin sublattice operators. Thermodynamical properties of this model are investigated in the molecular field approximation. The complete phase diagrams for all experimentally discovered collinear two-sublattice metamagnets are obtained numerically. Moreover some unknown kinds of phase diagrams are found, determining the new types of metamagnets which have not been experimentally observed so far. Finally, the theoretical results fitted for the FeCl2 and Mn3GaC, are compared with experiment.

Theory of collinear metamagnetism I: Unified treatment of field- and temperature-induced metamagnets☆

A magnetic field-pressure-temperature (H-P-T) phase diagram for first-order antiferromagnetic (AFM) to ferromagnetic (FM) transitions in Fe(49)(Rh(0.93)Pd(0.07))(51) has been constructed using resistivity measurements under simultaneous application of magnetic field (up to 8 T) and pressure (up to 20 kbar). The temperature dependence of resistivity (ρ-T) shows that the width of the transition and the extent of hysteresis decreases with pressure and increases with magnetic field. By exploiting opposing trends of dT(N)/dP and dT(N)/dH (where T(N) is the first-order transition temperature), the relative effects of temperature, magnetic field and pressure on disorder-broadened first-order transitions has been studied. For this, a set of H and P values are chosen for which T(N)(H(1),P(1)) = T(N)(H(2),P(2)). Measurements for such combinations of H and P show that the temperature dependence of resistivity is similar, i.e. the broadening (in temperature) of transition as well as the extent of hysteresis remains independent of H and P. Isothermal magnetoresistance measurements under various constant pressures show that even though the critical field required for AFM-FM transition depends on applied pressure, the extent of hysteresis as well as transition width (in magnetic field) remains constant with varying pressure.

https://iopscience.iop.org/article/10.1088/0953-8984/24/9/096005/pdf

D. Melville

Papers

High field magnetostriction in a meta-magnetic FeRh alloy