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

The first-order antiferromagnetic (AFM) to ferromagnetic (FM) transition in the functional material ${\text{Fe}}_{49}{\left({\text{Rh}}_{0.93}{\text{Pd}}_{0.07}\right)}_{51}$ 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.

Figure 1

(Color online) X-ray diffraction pattern for (a) as cast and (b) annealed sample. Peaks marked by stars $\left({}^{\ast }\right)$and vertical lines $(\mid )$ correspond to fct- and CsCl-type bcc structure, respectively.

Figure 2

(Color online) Resistivity behavior as a function of temperature for (a) as cast and (b) annealed sample. A first-order transition from FM (low-resistivity) to AFM (high-resistivity) state can be clearly seen in annealed sample.

Figure 3

(Color online) Temperature-dependent resistivity in different magnetic field conditions. Measurement has been performed during cooling (open symbol) and subsequent warming (solid symbol) in the presence of labeled magnetic field. $Y$ axis is for 0 T curve. For the sake of simplicity, other curves are shifted downward by labeled value, e.g., label $\left(\rho -30\right)$ indicates that resistivity curve is shifted by $30\mu \Omega \text{cm}$.

Figure 4

(Color online) Resistivity vs temperature in the presence of labeled magnetic field measured during warming. ZFCW curves were measured after cooling in zero-field and FCW curves were measured after cooling in same field value. The left inset shows the temperature dependence of magnetization in the presence of 6 T magnetic field. The right inset shows $\Delta {\rho }_{norm}$ at 5 K for FCW (star) and ZFCW (diamond) curve, highlighting the path dependence of FM and AFM phase fraction (see text for details).

Figure 5

(Color online) The magnetic field dependence of resistivity at various constant temperatures are shown in (a) below 50 K and (b) above 50 K. Increasing and decreasing magnetic field cycles are denoted by open and solid symbols, respectively. Upper right insets of both the graphs show the enlarged section of increasing field cycle whereas lower left inset correspond to decreasing field cycle. The forward curves $\left(0\to 14\text{T}\right)$ move to lower-field values monotonically with increasing temperature $\left(5\to 100\text{K}\right)$ as highlighted by the curved arrows. Whereas, the reverse curves $\left(14\text{T}\to 0\right)$ move nonmonotonically with temperature. Below/above 50 K, it shifts to higher/lower-field value with increasing temperature as highlighted by oppositely directed curved arrow in figures (a) and (b), respectively.

Figure 6

(Color online) $H\text{−}T$ phase diagram obtained from isothermal MR measurements shown in Fig. 5. Inset highlights the nonmonotonic variation in lower critical field and straight lines represent $\left(H_K,T_K\right)$ and $\left(H^{\ast },T^{\ast }\right)$ bands schematically.

Figure 7

(Color online) Resistivity as a function of temperature using CHUF protocol. Sample is cooled under different magnetic field of 0, 6, and 8 T, respectively, whereas measurement during warming are carried out in 6 T only. A reverse transformation from arrested FM to AFM at low temperature is clearly seen during heating in 6 T after 8 T field cooling only. The usual first-order AFM to FM transition is visible for all the warming curve for different field cooling. Inset shows the magnetization measured in the presence of 6 T magnetic field during warming after field cooling in the presence of 8 T magnetic field.