Selective Metal Exsolution in BaFe2-yMy(PO4)2 (M = Co2+, Ni2+) Solid Solutions

Ignacio Blazquez Alcover; Sylvie Daviero-Minaud; Rénald David; Dmitry Filimonov; Marielle Huvé; J. Paul Attfield; Houria Kabbour; Olivier Mentré

doi:10.1021/acs.inorgchem.5b01360

Selective Metal Exsolution in BaFe_2-yM_y(PO₄)₂ (M = Co²⁺, Ni²⁺) Solid Solutions

Ignacio Blazquez Alcover, Sylvie Daviero-Minaud, Rénald David, Dmitry Filimonov, Marielle Huvé, J. Paul Attfield, Houria Kabbour, Olivier Mentré^*

^*Corresponding author for this work

School of Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

The 2D-Ising ferromagnetic phase BaFe²⁺₂(PO₄)₂ shows exsolution of up to one-third of its iron content (giving BaFe³⁺_1.33(PO₄)₂) under mild oxidation conditions, leading to nanosized Fe₂O₃ exsolved clusters. Here we have prepared BaFe_2-yM_y(PO₄)₂ (M = Co²⁺, Ni²⁺; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600°C thermal treatment in air, a complete oxidation of Fe²⁺ to Fe³⁺ leaves stable M²⁺ ions, as verified by ⁵⁷Fe Mössbauer spectroscopy, TGA, TEM, microprobe, and XANES. The size of the nanometric α-Fe₂O₃ clusters coating the main phase strongly depends on the y_M metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe₂O₃ particles (100% for BaFe_0.5-xCo_1.5(PO₄)₂) was detected even at 78 K. Although Ni²⁺ and Co²⁺ ions tend to block Fe diffusion, the crystal structure of BaFe_0.67Co₁(PO₄)₂ demonstrates a fully ordered rearrangement of Fe³⁺ and Co²⁺ ions after Fe exsolution. The magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co²⁺-rich compounds show metamagnetic transitions reminiscent of the BaCo₂(PO₄)₂ soft helicoidal magnet. (Chemical Equation Presented).

Original language	English
Pages (from-to)	8733-8743
Number of pages	11
Journal	Inorganic Chemistry
Volume	54
Issue number	17
DOIs	https://doi.org/10.1021/acs.inorgchem.5b01360
Publication status	Published - 8 Sept 2015

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@article{787bfae021a3409caf0a1296fb874ac9,

title = "Selective Metal Exsolution in BaFe2-yMy(PO4)2 (M = Co2+, Ni2+) Solid Solutions",

abstract = "The 2D-Ising ferromagnetic phase BaFe2+2(PO4)2 shows exsolution of up to one-third of its iron content (giving BaFe3+1.33(PO4)2) under mild oxidation conditions, leading to nanosized Fe2O3 exsolved clusters. Here we have prepared BaFe2-yMy(PO4)2 (M = Co2+, Ni2+; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600°C thermal treatment in air, a complete oxidation of Fe2+ to Fe3+ leaves stable M2+ ions, as verified by 57Fe M{\"o}ssbauer spectroscopy, TGA, TEM, microprobe, and XANES. The size of the nanometric α-Fe2O3 clusters coating the main phase strongly depends on the yM metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe2O3 particles (100\% for BaFe0.5-xCo1.5(PO4)2) was detected even at 78 K. Although Ni2+ and Co2+ ions tend to block Fe diffusion, the crystal structure of BaFe0.67Co1(PO4)2 demonstrates a fully ordered rearrangement of Fe3+ and Co2+ ions after Fe exsolution. The magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co2+-rich compounds show metamagnetic transitions reminiscent of the BaCo2(PO4)2 soft helicoidal magnet. (Chemical Equation Presented).",

author = "\{Blazquez Alcover\}, Ignacio and Sylvie Daviero-Minaud and R{\'e}nald David and Dmitry Filimonov and Marielle Huv{\'e} and Attfield, \{J. Paul\} and Houria Kabbour and Olivier Mentr{\'e}",

year = "2015",

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day = "8",

doi = "10.1021/acs.inorgchem.5b01360",

language = "English",

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T1 - Selective Metal Exsolution in BaFe2-yMy(PO4)2 (M = Co2+, Ni2+) Solid Solutions

AU - Blazquez Alcover, Ignacio

AU - Daviero-Minaud, Sylvie

AU - David, Rénald

AU - Filimonov, Dmitry

AU - Huvé, Marielle

AU - Attfield, J. Paul

AU - Kabbour, Houria

AU - Mentré, Olivier

PY - 2015/9/8

Y1 - 2015/9/8

N2 - The 2D-Ising ferromagnetic phase BaFe2+2(PO4)2 shows exsolution of up to one-third of its iron content (giving BaFe3+1.33(PO4)2) under mild oxidation conditions, leading to nanosized Fe2O3 exsolved clusters. Here we have prepared BaFe2-yMy(PO4)2 (M = Co2+, Ni2+; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600°C thermal treatment in air, a complete oxidation of Fe2+ to Fe3+ leaves stable M2+ ions, as verified by 57Fe Mössbauer spectroscopy, TGA, TEM, microprobe, and XANES. The size of the nanometric α-Fe2O3 clusters coating the main phase strongly depends on the yM metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe2O3 particles (100% for BaFe0.5-xCo1.5(PO4)2) was detected even at 78 K. Although Ni2+ and Co2+ ions tend to block Fe diffusion, the crystal structure of BaFe0.67Co1(PO4)2 demonstrates a fully ordered rearrangement of Fe3+ and Co2+ ions after Fe exsolution. The magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co2+-rich compounds show metamagnetic transitions reminiscent of the BaCo2(PO4)2 soft helicoidal magnet. (Chemical Equation Presented).

AB - The 2D-Ising ferromagnetic phase BaFe2+2(PO4)2 shows exsolution of up to one-third of its iron content (giving BaFe3+1.33(PO4)2) under mild oxidation conditions, leading to nanosized Fe2O3 exsolved clusters. Here we have prepared BaFe2-yMy(PO4)2 (M = Co2+, Ni2+; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600°C thermal treatment in air, a complete oxidation of Fe2+ to Fe3+ leaves stable M2+ ions, as verified by 57Fe Mössbauer spectroscopy, TGA, TEM, microprobe, and XANES. The size of the nanometric α-Fe2O3 clusters coating the main phase strongly depends on the yM metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe2O3 particles (100% for BaFe0.5-xCo1.5(PO4)2) was detected even at 78 K. Although Ni2+ and Co2+ ions tend to block Fe diffusion, the crystal structure of BaFe0.67Co1(PO4)2 demonstrates a fully ordered rearrangement of Fe3+ and Co2+ ions after Fe exsolution. The magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co2+-rich compounds show metamagnetic transitions reminiscent of the BaCo2(PO4)2 soft helicoidal magnet. (Chemical Equation Presented).

UR - https://www.scopus.com/pages/publications/84941286918

U2 - 10.1021/acs.inorgchem.5b01360

DO - 10.1021/acs.inorgchem.5b01360

M3 - Article

AN - SCOPUS:84941286918

SN - 0020-1669

VL - 54

SP - 8733

EP - 8743

JO - Inorganic Chemistry

JF - Inorganic Chemistry

IS - 17

ER -

Selective Metal Exsolution in BaFe_2-yM_y(PO₄)₂ (M = Co²⁺, Ni²⁺) Solid Solutions

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