Effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite ${\left({\text{La}}_{0.4}{\text{Pr}}_{0.6}\right)}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_2{\text{O}}_7$

We report the effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite ${\left({\text{La}}_{0.4}{\text{Pr}}_{0.6}\right)}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_2{\text{O}}_7$, for our understanding of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase. The application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. The injection of an electric current to the crystal also weakens the steplike variation in both the magnetostriction and magnetoresistance. The stabilization of ferromagnetic interaction or the delocalization of charge carriers is promoted with the applied pressure or applied current, resulting in the suppressed steplike behavior. Our findings suggest that the step phenomenon is closely related to the existence of localized carriers such as the short-range charge-orbital-ordered clusters.

Figure 1

(Color online) The $c$-axis magnetostriction, $d{L}_c\left(H\right)/L_c\left(0\right)$, of ${\left({\text{La}}_{0.4}{\text{Pr}}_{0.6}\right)}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_2{\text{O}}_7$, under both ambient pressure and a hydrostatic pressure of 0.8 GPa at low temperatures of (a) 4 and (b) 6 K. The applied field is parallel to the $c$ axis $\left(H\parallel c\right)$.

Figure 2

(Color online) The $c$-axis magnetostriction, $d{L}_c\left(H\right)/L_c\left(0\right)$, of ${\left({\text{La}}_{0.4}{\text{Pr}}_{0.6}\right)}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_2{\text{O}}_7$, under both ambient pressure and a hydrostatic pressure of 0.8 GPa at 20 K: (a) $H\parallel c$ and (b) $H\parallel ab$.

Figure 3

(Color online) The $c$-axis magnetostriction, $d{L}_c\left(H\right)/L_c\left(0\right)$, of ${\left({\text{La}}_{0.4}{\text{Pr}}_{0.6}\right)}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_2{\text{O}}_7$, under both ambient pressure and a hydrostatic pressure of 0.8 GPa at low temperatures of (a) 4, (b) 6, and (c) 8 K. The applied field is parallel to the $ab$ plane $\left(H\parallel ab\right)$.

Figure 4

(Color online) The $c$-axis magnetostriction, $d{L}_c\left(H\right)/L_c\left(0\right)$, of ${\left({\text{La}}_{0.4}{\text{Pr}}_{0.6}\right)}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_2{\text{O}}_7$, under the electric current applied on the $ab$ plane at low temperatures of (a) 4 and (b) 6 K. The applied field is parallel to the $c$ axis. (c) The $ab$-plane magnetoresistance $R_{ab}$ of the $z=0.6$ sample at 4.3 K as a function of the applied current from 0.1 up to 2.5 mA. The $R_{ab}\left(\text{H}\right)$ data are normalized by $R_{ab}\left(0\right)$, which is the zero-field resistance at the lowest applied current (0.1 mA); $\left(H\parallel c\right)$.