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Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO 3

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ABSTRACT

We synthesize ScCoO3 perovskite and its solid solutions, ScCo1−xFexO3 and ScCo1−xCrxO3, under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc1−xMx)MO3 with x = 0.05–0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc0.95Co0.05)CoO3 is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc0.95Co0.05)CoO3 crystallizes in the GdFeO3-type structure similar to other members of the perovskite cobaltite family, ACoO3 (A3+ = Y and Pr-Lu). There is evidence that (Sc0.95Co0.05)CoO3 has non-magnetic low-spin Co3+ ions at the B site and paramagnetic high-spin Co3+ ions at the A site. In the iron-doped samples (Sc1−xMx)MO3 with M = (Co, Fe), Fe3+ ions have a strong preference to occupy the A site of such perovskites at small doping levels.

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ZFC (filled symbols) and FCC (empty symbols) uncorrected magnetic susceptibility (χ = M/H) curves at 100 Oe and 70 kOe for (a) (Sc0.95Co0.05)CoO3 and (b) (Sc0.95M0.05)MO3 ( The right-hand axes give inverse FCC curves (χ−1 versus T) at 70 kOe. Parameters (μeff and θ) of the Curie–Weiss fits (bold lines) between 300 and 400 K are given. The thin lines show the same FCC χ−1 versus T curves at 70 kOe corrected for contributions from diamagnetic sample holders and core diamagnetism.
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Figure 3: ZFC (filled symbols) and FCC (empty symbols) uncorrected magnetic susceptibility (χ = M/H) curves at 100 Oe and 70 kOe for (a) (Sc0.95Co0.05)CoO3 and (b) (Sc0.95M0.05)MO3 ( The right-hand axes give inverse FCC curves (χ−1 versus T) at 70 kOe. Parameters (μeff and θ) of the Curie–Weiss fits (bold lines) between 300 and 400 K are given. The thin lines show the same FCC χ−1 versus T curves at 70 kOe corrected for contributions from diamagnetic sample holders and core diamagnetism.

Mentions: We observed no difference between the ZFC and FCC curves measured at low magnetic fields (e.g., 0.1 kOe) and high magnetic fields (e.g., 70 kOe) (figure 3(a)). At high temperatures, almost no difference was found in magnetic susceptibilities measured at 0.1 and 70 kOe; however, at low temperatures, magnetic susceptibilities were suppressed by high magnetic fields in agreement with the isothermal M versus H curves (figure 4(a)). (Sc0.95Co0.05)CoO3 exhibits paramagnetic behaviour (figure 3(a)) with a relatively large effective magnetic moment of μeff = 1.749(6)μB/f.u. (μB is the Bohr magneton and f.u. is the formula unit) and the Curie–Weiss temperature of θ = −130(3) K. It is expected that Co3+ ions at the B site should be in the non-magnetic low-spin (LS) state similar to other members of the ACoO3 (A3+ = Y and Pr-Lu) family [6, 26]; the temperature of the spin-state (LS-to-HS) transition increases sharply with decreasing the size of the A type cation [6]. Therefore, a large effective magnetic moment should originate from the high-spin Co3+ ions located at the A site. The expected calculated effective magnetic moment is 1.124μB (for 0.0526Co3+), which is close to the experimentally obtained value. Large effective magnetic moments and Curie–Weiss temperatures were also observed in LaCo1−xMxO3 (M = Rh and Ir) [27]; μeff for the impurity-related magnetism is usually one order of magnitude smaller [28]. Magnetic properties of (Sc0.95M0.05)MO3 ( were very similar with those of (Sc0.95Co0.05)CoO3 (figure 3(b)), with a slightly larger μeff = 2.050(4)μB/f.u. because of the presence of Fe3+ ions (the expected μeff is about 1.63μB). Note that the intrinsic magnetic moment of (Sc0.95Co0.05)CoO3 is quite small at high temperatures; therefore, diamagnetic contributions (from sample holders and core diamagnetism) have a significant influence on the μeff and θ values (figure 3) making it difficult to discuss them.


Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO 3
ZFC (filled symbols) and FCC (empty symbols) uncorrected magnetic susceptibility (χ = M/H) curves at 100 Oe and 70 kOe for (a) (Sc0.95Co0.05)CoO3 and (b) (Sc0.95M0.05)MO3 ( The right-hand axes give inverse FCC curves (χ−1 versus T) at 70 kOe. Parameters (μeff and θ) of the Curie–Weiss fits (bold lines) between 300 and 400 K are given. The thin lines show the same FCC χ−1 versus T curves at 70 kOe corrected for contributions from diamagnetic sample holders and core diamagnetism.
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Figure 3: ZFC (filled symbols) and FCC (empty symbols) uncorrected magnetic susceptibility (χ = M/H) curves at 100 Oe and 70 kOe for (a) (Sc0.95Co0.05)CoO3 and (b) (Sc0.95M0.05)MO3 ( The right-hand axes give inverse FCC curves (χ−1 versus T) at 70 kOe. Parameters (μeff and θ) of the Curie–Weiss fits (bold lines) between 300 and 400 K are given. The thin lines show the same FCC χ−1 versus T curves at 70 kOe corrected for contributions from diamagnetic sample holders and core diamagnetism.
Mentions: We observed no difference between the ZFC and FCC curves measured at low magnetic fields (e.g., 0.1 kOe) and high magnetic fields (e.g., 70 kOe) (figure 3(a)). At high temperatures, almost no difference was found in magnetic susceptibilities measured at 0.1 and 70 kOe; however, at low temperatures, magnetic susceptibilities were suppressed by high magnetic fields in agreement with the isothermal M versus H curves (figure 4(a)). (Sc0.95Co0.05)CoO3 exhibits paramagnetic behaviour (figure 3(a)) with a relatively large effective magnetic moment of μeff = 1.749(6)μB/f.u. (μB is the Bohr magneton and f.u. is the formula unit) and the Curie–Weiss temperature of θ = −130(3) K. It is expected that Co3+ ions at the B site should be in the non-magnetic low-spin (LS) state similar to other members of the ACoO3 (A3+ = Y and Pr-Lu) family [6, 26]; the temperature of the spin-state (LS-to-HS) transition increases sharply with decreasing the size of the A type cation [6]. Therefore, a large effective magnetic moment should originate from the high-spin Co3+ ions located at the A site. The expected calculated effective magnetic moment is 1.124μB (for 0.0526Co3+), which is close to the experimentally obtained value. Large effective magnetic moments and Curie–Weiss temperatures were also observed in LaCo1−xMxO3 (M = Rh and Ir) [27]; μeff for the impurity-related magnetism is usually one order of magnitude smaller [28]. Magnetic properties of (Sc0.95M0.05)MO3 ( were very similar with those of (Sc0.95Co0.05)CoO3 (figure 3(b)), with a slightly larger μeff = 2.050(4)μB/f.u. because of the presence of Fe3+ ions (the expected μeff is about 1.63μB). Note that the intrinsic magnetic moment of (Sc0.95Co0.05)CoO3 is quite small at high temperatures; therefore, diamagnetic contributions (from sample holders and core diamagnetism) have a significant influence on the μeff and θ values (figure 3) making it difficult to discuss them.

View Article: PubMed Central - PubMed

ABSTRACT

We synthesize ScCoO3 perovskite and its solid solutions, ScCo1−xFexO3 and ScCo1−xCrxO3, under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc1−xMx)MO3 with x = 0.05–0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc0.95Co0.05)CoO3 is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc0.95Co0.05)CoO3 crystallizes in the GdFeO3-type structure similar to other members of the perovskite cobaltite family, ACoO3 (A3+ = Y and Pr-Lu). There is evidence that (Sc0.95Co0.05)CoO3 has non-magnetic low-spin Co3+ ions at the B site and paramagnetic high-spin Co3+ ions at the A site. In the iron-doped samples (Sc1−xMx)MO3 with M = (Co, Fe), Fe3+ ions have a strong preference to occupy the A site of such perovskites at small doping levels.

No MeSH data available.


Related in: MedlinePlus