Magnetic properties of $(\mathrm{Nd},\mathrm{Ca})\left(\mathrm{Ba},\mathrm{La}\right)\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ tuned by the site-selected charge doping, oxygen disorder, and hydrostatic pressure

Comprehensive study of magnetic properties of the layer-ordered perovskites $\mathrm{N}{\mathrm{d}}_{1–x}\mathrm{C}{\mathrm{a}}_x\mathrm{B}{\mathrm{a}}_{1–y}\mathrm{L}{\mathrm{a}}_y\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ is presented as a function of the site-selected charge doping $\mathrm{[}c=\left(x–y\right)/2+\delta -0.5,x\le 0.2$ and $y\le 0.1,0.07<\delta <0.84]$, oxygen disorder, and hydrostatic pressure $P<10\mathrm{kbar}$. The single-phase oxygen-ordered orthorhombic phase exhibiting complex ferrimagnetic, antiferromagnetic, and metal-insulator phase transitions was found for a narrow oxygen range around $\delta \sim 0.5\pm 0.1$. Significant difference between impact of hole $\left(c>0\right)$ and electron $\left(c<0\right)$ doping was observed depending on the site of cation substitution. Gradual enhancement of the Curie temperature $T_{\mathrm{C}}$ was observed over the whole range of $c$ to be unaffected by the local oxygen vacancy disorder. Maximum of the Néel temperature $T_{\mathrm{N}}$ at $c=0$ was found rapidly disappearing at $c=0.05$ for Ca/Nd substitution while it was maintained for La/Ba substitution, indicating that the oxygen vacancy disorder, especially for $\delta >0.5$, has a larger effect on antiferromagnetic phase than the charge doping. The temperature of metal-insulator transition $T_{\mathrm{MIT}}$ was found practically unchanged by either charge doping or disorder. The application of hydrostatic pressure slightly suppressed $T_{\mathrm{C}}$ and increased $T_{\mathrm{N}}$ by stabilization of the antiferromagnetic phase with the largest observed value of $\mathrm{d}{T}_{\mathrm{N}}/\mathrm{d}P=5.75\mathrm{K}/\mathrm{kbar}$. Complex magnetic behavior affected by hydrostatic pressure was accounted for by ferro- and antiferromagnetic interactions resulting from the charge separation and spin transitions.

Figure 1

Crystal structure of $\mathrm{N}{\mathrm{d}}_{1–x}\mathrm{C}{\mathrm{a}}_x\mathrm{B}{\mathrm{a}}_{1–y}\mathrm{L}{\mathrm{a}}_y\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$.

Figure 2

Lattice parameters as a function of oxygen content for $\mathrm{NdB}{\mathrm{a}}_{0.9}\mathrm{L}{\mathrm{a}}_{0.1}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ (a), $\mathrm{NdB}{\mathrm{a}}_{0.94}\mathrm{L}{\mathrm{a}}_{0.06}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ (b), $\mathrm{N}{\mathrm{d}}_{0.94}\mathrm{C}{\mathrm{a}}_{0.06}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ (c), and $\mathrm{N}{\mathrm{d}}_{0.9}\mathrm{C}{\mathrm{a}}_{0.1}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ (d). Open symbols are lattice parameters for $\mathrm{NdBaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ crystals from Ref. [15]. Panel (e) shows the range of oxygen index (marked by solid lines) associated with crystallization in the Pmmm space group. The data for $\mathrm{NdBaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ (red line at the center of the figure) are taken from Ref. [15].

Figure 3

(a) Temperature dependences of magnetization for $\mathrm{NdB}{\mathrm{a}}_{1–y}\mathrm{L}{\mathrm{a}}_y\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5.5}$ with $y=0$, 0.06, and 0.1. (b) Phase diagram in which PM-M is the paramagnetic metallic phase, PM-I is the PM insulating phase, FM-I is the ferrimagnetic insulating phase, and AFM-I is the AFM insulating phase. The main transition temperatures $T_{\mathrm{MIT}},T_{\mathrm{C}}$, and $T_{\mathrm{N}}$ are plotted. (c) Temperature dependences of magnetization for $\mathrm{NdB}{\mathrm{a}}_{0.9}\mathrm{L}{\mathrm{a}}_{0.1}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ with selected oxygen contents. Inset shows the same data in the vicinity of $T_{\mathrm{MIT}}$. Panel (d) shows oxygen content dependence of main transition temperatures $T_{\mathrm{N}},T_{\mathrm{C}}$, and $T_{\mathrm{MIT}}$ for $\mathrm{NdB}{\mathrm{a}}_{0.9}\mathrm{L}{\mathrm{a}}_{0.1}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$. Closed symbols refer to the transitions in orthorhombic phase, while the open symbols refer to the transitions beyond orthorhombic phase.

Figure 4

Temperature dependences of ZFC and FC magnetization of $\mathrm{NdB}{\mathrm{a}}_{0.9}\mathrm{L}{\mathrm{a}}_{0.1}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ measured at 1 kOe for $\delta =0.5$ (a), $\delta =0.53$ (b), and $\delta =0.54$ (c) at ambient and under hydrostatic pressure. Insets show magnetic field dependences of magnetization for $\mathrm{NdB}{\mathrm{a}}_{0.9}\mathrm{L}{\mathrm{a}}_{0.1}\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ measured at 150 K, using the FC procedure in 50 kOe at ambient and under hydrostatic pressure.

Figure 5

Temperature dependences of magnetization for $\mathrm{N}{\mathrm{d}}_{0.94}\mathrm{C}{\mathrm{a}}_{0.06}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ with selected oxygen contents (a). Panel (b) shows oxygen content dependence of main transition temperatures $T_{\mathrm{N}},T_{\mathrm{C}}$, and $T_{\mathrm{MIT}}$ for $\mathrm{N}{\mathrm{d}}_{0.94}\mathrm{C}{\mathrm{a}}_{0.06}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$. Closed symbols refer to the transitions in orthorhombic phase, while the open symbols refer to the transitions beyond orthorhombic phase.

Figure 6

Temperature dependences of ZFC and FC magnetization of $\mathrm{N}{\mathrm{d}}_{0.94}\mathrm{C}{\mathrm{a}}_{0.06}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ measured at 1 kOe for selected δ index at ambient and under hydrostatic pressure (a). Panel (b) shows magnetic field dependences of magnetization for $\mathrm{N}{\mathrm{d}}_{0.94}\mathrm{C}{\mathrm{a}}_{0.06}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ for selected δ index, measured using the FC procedure in 50 kOe at ambient and under hydrostatic pressure.

Figure 7

(a) Temperature dependences of magnetization for $\mathrm{N}{\mathrm{d}}_{0.9}\mathrm{C}{\mathrm{a}}_{0.1}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ with selected oxygen contents (after Ref. [11]). Panel (b) shows oxygen content dependence of main transition temperatures $T_{\mathrm{N}},T_{\mathrm{C}}$, and $T_{\mathrm{MIT}}$ for $\mathrm{N}{\mathrm{d}}_{0.9}\mathrm{C}{\mathrm{a}}_{0.1}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$. Closed symbols refer to the transitions in orthorhombic phase, while the open symbols refer to the transitions beyond orthorhombic phase.

Figure 8

(a) Temperature dependences of ZFC and FC magnetization of $\mathrm{N}{\mathrm{d}}_{0.9}\mathrm{C}{\mathrm{a}}_{0.1}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ measured at 1 kOe for selected δ index at ambient and under hydrostatic pressure. (b) Magnetic field dependences of magnetization for $\mathrm{N}{\mathrm{d}}_{0.9}\mathrm{C}{\mathrm{a}}_{0.1}\mathrm{BaC}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$ for selected oxygen contents, measured using the FC procedure in 50 kOe at ambient and under hydrostatic pressure.

Figure 9

(a) Phase diagram of $(\mathrm{Nd},\mathrm{Ca})\left(\mathrm{Ba},\mathrm{La}\right)\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$, in which PM-M is the paramagnetic metallic phase, PM-I is the paramagnetic insulating phase, FM-I is the ferrimagnetic insulating phase, and AFM-I is the antiferromagnetic insulating phase. The main transition temperatures $T_{\mathrm{N}},T_{\mathrm{C}}$, and $T_{\mathrm{MIT}}$ are plotted. Panel (b) shows oxygen content dependence of $T_{\mathrm{C}}$ for $(\mathrm{Nd},\mathrm{Ca})\left(\mathrm{Ba},\mathrm{La}\right)\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$. Panel (c) shows oxygen content dependence of $T_{\mathrm{N}}$ for $(\mathrm{Nd},\mathrm{Ca})\left(\mathrm{Ba},\mathrm{La}\right)\mathrm{C}{\mathrm{o}}_2{\mathrm{O}}_{5+\delta }$. Panel (d) shows δ dependence of main transition temperatures at fixed selected values of carrier doping parameter $c$.