Coupled structural collapse and evolution of magnetic phases in Sr(Co 0.88 Ni 0.12 ) 2 P 2 under pressure

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Abstract
We report high-pressure x-ray diffraction and electrical resistance measurements on Sr(Co 0.88 Ni 0.12 ) 2 P 2 , an itinerant antiferromagnet with the highest Néel temperature ( T N = 36 K) among Sr(Co 1 − x Ni x ) 2 P 2 series. Room-temperature diffraction data reveal a pressure-induced transition from an uncollapsed tetragonal to a collapsed tetragonal (cT) structure, beginning near 8.4 GPa and completing before 12.4 GPa. This transition is characterized by an expansion of the in-plane a -lattice parameter and a contraction in the c -lattice parameter, resulting in a reduction of the axial ratio c / a . Resistance measurements show a low-pressure anomaly near 38 K, consistent with the reported antiferromagnetic transition. As the room temperature value of the applied pressure exceeds 8 GPa, signs of a partial cT transition appear on cooling with the full cT transition occurring for pressures exceeding 10 GPa. The cT phase is accompanied by a much higher-temperature transport anomaly that resembles the pressure-induced ferromagnetic transition reported for SrCo 2 P 2 , reaching approximately 190 K before gradually decreasing at higher pressures. These results demonstrate strong coupling between the lattice collapse and magnetic behavior in Sr(Co 0.88 Ni 0.12 ) 2 P 2 .
Funding Information
  • Directorate for Geosciences (EAR-2223273)
  • Basic Energy Sciences (DE-AC02-07CH11358)
  • National Science Foundation (DMR-2606278)
  • Argonne National Laboratory

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