Large magnetoresistance in the magnetically ordered state as well as in the paramagnetic state near 300 K in an intermetallic compound,Gd7Rh3

We report the response of electrical resistivity $\rho$ to the application of magnetic fields (H) up to 140 kOe in the temperature interval 1.8-300 K for the compound, Gd7Rh3, ordering antiferromagnetically below 150 K. We find that there is an unusually large decrease of $\rho$ for moderate values of H in the close vicinity of room temperature uncharacteristic of paramagnets, with the magnitude of the magnetoresistance increasing with decreasing temperature as though the spin-order contribution to $\rho$ is temperature dependent. In addition, this compound exhibits giant magnetoresistance behaviour at rather high temperatures (above 77 K) in the magnetically ordered state due to a metamagnetic transition.Comment: Europhyics Letters, in pres

Field-induced first-order magnetic phase transition in an intermetallic compound, Nd7Rh3: Evidence for kinetic-hindrance, phase co-existence and percolative conduction

The compound, Nd7Rh3, crystallizing in Th7Fe3-type hexagonal structure, was previously known to exhibit two magnetic transitions, one at 32 K and the other at 10 K (in zero magnetic field). Here, we report the existence of a field-induced first-order antiferromagnetic to ferromagnetic transition at 1.8 K in this compound. On the basis of the measurements of isothermal magnetization and magnetoresistance, we provide evidence for the occurence of kinetic-hindrance, proposed in the literature, resulting in phase co-existence (super-cooled ferromagnetic + antifferomagnetic) and percolative electrical conduction in this stoichiometric intermetallic compound. A point of emphasis, as inferred from ac susceptibility data, is that such a co-existing phase is different from spin-glasses, thereby clarifying a question raised in the field of phase-separation.Comment: A Shortened version will appear in print in PRB (Rapid Comm). Phys. Rev. B (Rapid Comm), in pres

Large magnetoresistance anomalies in Dy7Rh3

The compound Dy7Rh3 ordering antiferromagnetically below (TN=) 59 K has been known to exhibit a temperature (T) dependent electrical resistivity (rho) behavior in the paramagnetic state unusual for intermetallic compounds in the sense that there is a broad peak in rho(T) in the paramagnetic state (around 130 K) as though there is a semi-conductor to metal transition. In addition, there is an upturn below T_N due to magnetic super-zone gap effects. Here we report the influence of external magnetic field (H) on the rho(T) behavior of this compound below 300 K. The rise of rho(T) found below TN could be suppressed at very high fields (>> 60 kOe), thus resulting in a very large magnetoresistance (MR) in the magnetically ordered state. The most notable finding is that the magnitude of MR is large for moderate applications of H (say 80 kOe) in a temperature range far above T_N as well, which is untypical of intermetallic compounds. Thus, this compound is characterized by large MR anomalies in the entire T range of investigation.Comment: IOP Selec