Title: Pressure control of magnetic order and excitations in the pyrochlore antiferromagnet ${\mathrm{MgCr}}_2{\mathrm{O}}_4$

Abstract

MgCr₂O₄ is one of the best-known realizations of the pyrochlore-lattice Heisenberg antiferromagnet. The strong antiferromagnetic exchange interactions are perturbed by small further-neighbor exchanges such that this compound may in principle realize a spiral spin liquid (SSL) phase in the zero-temperature limit. However, a spin Jahn-Teller transition below T_N ≈ 13 K yields a complicated long-range magnetic order with multiple coexisting propagation vectors. We present neutron scattering and thermomagnetic measurements of MgCr₂O₄ samples under applied hydrostatic pressure up to P = 1.7 GPa demonstrating the existence of multiple close-lying nearly degenerate magnetic ground states. We show that the application of hydrostatic pressure increases the ordering temperature by around 0.8 K per GPa and increases the bandwidth of the magnetic excitations by around 0.5 meV per GPa. We also evidence a strong tendency for the preferential occupation of a subset of magnetic domains under pressure. In particular, we show that the $$k$$ = (0,0,1) magnetic phase, which is almost negligible at ambient pressure, dramatically increases in spectral weight under pressure. This modifies the spectrum of magnetic excitations, which we interpret unambiguously as spin waves from multiple magnetic domains. Moreover, we report that the application of pressure reveals a feature in the magnetic susceptibility above the magnetostructural transition. We interpret this as the onset of a short-range ordered phase associated with $$k$$ = (0,0,1), previously not observed in magnetometry measurements.

Authors:

Nassar, L. S. ;

• Search DOE PAGES for author "Nassar, L. S."
• Search DOE PAGES for ORCID "0000-0002-7517-2865"

Lane, H.; Haberl, B. ;

• Search DOE PAGES for author "Haberl, B."
• Search DOE PAGES for ORCID "0000-0002-7391-6031"

Graves-Brook, M.; Winn, B.; Koohpayeh, S. M.; Mourigal, M.

• Search DOE PAGES for author "Mourigal, M."
• Search DOE PAGES for ORCID "0000-0003-2772-8440"

Publication Date:

Fri Feb 16 00:00:00 EST 2024

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Georgia Institute of Technology, Atlanta, GA (United States); Johns Hopkins Univ., Baltimore, MD (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); National Science Foundation (NSF)

OSTI Identifier:

2305792

Alternate Identifier(s):

OSTI ID: 2317752

Grant/Contract Number:  

SC-0018660; AC05-00OR22725; SC0018660; SC0019331; ECCS-2025462

Resource Type:

Published Article

Journal Name:

Physical Review. B

Additional Journal Information:

Journal Name: Physical Review. B Journal Volume: 109 Journal Issue: 6; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY