Peculiar magnetic states in the double perovskite Nd2NiMnO6

Somnath Pal, Somnath Jana, Sharada Govinda, Banabir Pal, Sumanta Mukherjee, Samara Keshavarz, Danny Thonig, Yaroslav Kvashnin, Manuel Pereiro, Roland Mathieu, Per Nordblad, John W. Freeland, Olle Eriksson, Olof Karis, and D. D. Sarma
Phys. Rev. B 100, 045122 – Published 16 July 2019

Abstract

We present magnetic measurements on Nd2NiMnO6 which exhibits a well-known insulating paramagnetic state to an insulating ferromagnetic state transition when cooled below 200 K. Beyond this basic fact, there is a great deal of diversity in the reported magnetic properties and interpretation of specific anomalies observed in the magnetic data of this compound below the Curie temperature. We address specifically two anomalies discussed in the past, namely, a spin-glass like behavior observed in some samples near 100 K and a downturn in the magnetization with a lowering of the temperature below approximately 50 K. We show for the first time that the application of an increasing magnetic field can systematically change the low-temperature behavior to make the down-turn in the magnetization into an upturn. With the help of first principle calculations and extensive simulations along with our experimental observations, we provide a microscopic understanding of all magnetic properties observed in this interesting system to point out that the glassiness around 100 K is absent in well-ordered samples and that the low-temperature magnetic anomaly below 50 K is a consequence of a ferromagnetic coupling of the Nd spin moments with the spin of the Ni-Mn ordered sublattice without giving rise to any ordering of the Nd sublattice that remains paramagnetic, contrary to earlier claims. We explain this counter-intuitive interpretation of a ferromagnetic coupling of Nd spins with Ni-Mn spin giving rise to a decrease in the total magnetic moment by noting the less than half-filled 4f occupation of Nd that ensures orbital and spin moments of Nd to be opposite to each other due to the spin-orbit coupling. Since the ground state total magnetic moment of Nd has a contribution from the orbital moment, that is larger than the spin moment, the total moment of Nd is indeed pointing in a direction opposite to the direction of spin moments of the Ni-Mn sublattice as a consequence of the ferromagnetic exchange coupling between Nd and Ni-Mn spins.

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  • Received 8 November 2018
  • Revised 25 June 2019

DOI:https://doi.org/10.1103/PhysRevB.100.045122

©2019 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
  1. Physical Systems
Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Somnath Pal1, Somnath Jana2,*, Sharada Govinda1, Banabir Pal1, Sumanta Mukherjee1, Samara Keshavarz2, Danny Thonig2, Yaroslav Kvashnin2, Manuel Pereiro2, Roland Mathieu3, Per Nordblad3, John W. Freeland4, Olle Eriksson2,5, Olof Karis2, and D. D. Sarma1,†

  • 1Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, India
  • 2Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
  • 3Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden
  • 4Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 5School of Science and Technology, Örebro University, SE-70182 Örebro, Sweden

  • *Present Address: Institute for Methods and Instrumentation in Synchrotron Radiation Research FG-ISRR, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
  • Also at Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru; sarma@iisc.ac.in

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Issue

Vol. 100, Iss. 4 — 15 July 2019

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