Pressure-Driven Transitions in La2CoTiO6: Antiferromagnetic Insulator to Nonmagnetic Metal via Antiferromagnetic Metal in a Double Perovskite Oxide
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2023
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| _version_ | 1866910568435154944 |
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| author | Nandi, Sromona Pradhan, Subhadip Nandy, Ashis K. Manna, Rudra Sekhar |
| author_facet | Nandi, Sromona Pradhan, Subhadip Nandy, Ashis K. Manna, Rudra Sekhar |
| contents | In double perovskite oxides (A$_2$BB$^\prime$O$_6$), magnetism often arises from diluted magnetic lattices, created by combining a perovskite structure with localized 3$d$ magnetic elements (B) alongside another perovskite lattice containing nearly nonmagnetic delocalized 4$d$/$5d$ elements (B$^\prime$). Alternatively, the magnetic lattice can consist entirely of 3$d$ elements, with one being completely nonmagnetic with $d^0$ state. La$_2$CoTiO$_6$ (LCTO), a representative double perovskite oxide, contains Ti in a nonmagnetic state with a $d^0$ electron configuration due to its $4^+$ oxidation state. Experimental evidence shows that LCTO possesses a monoclinic structure (space group $P2_1/n$) and behaves as an antiferromagnet with a Néel temperature of 14.6 K. Through first-principle electronic structure calculations, we uncover that adjusting external hydrostatic pressure induces a sequence of phase transitions: from antiferromagnetic insulator (AFM-I) to antiferromagnetic metal (AFM-M), and ultimately to itinerant nonmagnetic metal (NM-M). The transition from AFM-I to AFM-M at $\sim$ 42 GPa pressure coincides with a shift in spin states, moving from a high-spin (HS) state to a low-spin (LS) state, while Co retains a $d^7$ configuration. Distortion within the monoclinic structure under pressure plays a pivotal role in the spin-state transition. At the AFM-I to AFM-M transition, we observe a sharp decrease in the ratio of the octahedral volumes occupied by Co and Ti. Such change in ratio is linked to variations in octahedral volumes, akin to a breathing mode distortion. We explore the impact of the breathing mode distortion by examining a highly symmetric theoretical structure (space-group $I4/mmm$), achieved by optimizing the structure with all $\angle${Co-O-Ti} angles set to 180$^{\circ}$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2310_05523 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Pressure-Driven Transitions in La2CoTiO6: Antiferromagnetic Insulator to Nonmagnetic Metal via Antiferromagnetic Metal in a Double Perovskite Oxide Nandi, Sromona Pradhan, Subhadip Nandy, Ashis K. Manna, Rudra Sekhar Strongly Correlated Electrons Materials Science In double perovskite oxides (A$_2$BB$^\prime$O$_6$), magnetism often arises from diluted magnetic lattices, created by combining a perovskite structure with localized 3$d$ magnetic elements (B) alongside another perovskite lattice containing nearly nonmagnetic delocalized 4$d$/$5d$ elements (B$^\prime$). Alternatively, the magnetic lattice can consist entirely of 3$d$ elements, with one being completely nonmagnetic with $d^0$ state. La$_2$CoTiO$_6$ (LCTO), a representative double perovskite oxide, contains Ti in a nonmagnetic state with a $d^0$ electron configuration due to its $4^+$ oxidation state. Experimental evidence shows that LCTO possesses a monoclinic structure (space group $P2_1/n$) and behaves as an antiferromagnet with a Néel temperature of 14.6 K. Through first-principle electronic structure calculations, we uncover that adjusting external hydrostatic pressure induces a sequence of phase transitions: from antiferromagnetic insulator (AFM-I) to antiferromagnetic metal (AFM-M), and ultimately to itinerant nonmagnetic metal (NM-M). The transition from AFM-I to AFM-M at $\sim$ 42 GPa pressure coincides with a shift in spin states, moving from a high-spin (HS) state to a low-spin (LS) state, while Co retains a $d^7$ configuration. Distortion within the monoclinic structure under pressure plays a pivotal role in the spin-state transition. At the AFM-I to AFM-M transition, we observe a sharp decrease in the ratio of the octahedral volumes occupied by Co and Ti. Such change in ratio is linked to variations in octahedral volumes, akin to a breathing mode distortion. We explore the impact of the breathing mode distortion by examining a highly symmetric theoretical structure (space-group $I4/mmm$), achieved by optimizing the structure with all $\angle${Co-O-Ti} angles set to 180$^{\circ}$. |
| title | Pressure-Driven Transitions in La2CoTiO6: Antiferromagnetic Insulator to Nonmagnetic Metal via Antiferromagnetic Metal in a Double Perovskite Oxide |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2310.05523 |