Microscopic characterization of the magnetic properties of the itinerant antiferromagnet La 2 Ni 7 by La 139 NMR/NQR measurements

Journal Article · 10 August 2023 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.108.064413 · OSTI ID:1994521

Ding, Qing -Ping  ^[1]; Babu, Joyal  ^[2]; Rana, K. ^[1]; Lee, Yongbin  ^[1]; Bud'ko, S. L. ^[2]; Ribeiro, R. A. ^[2]; Canfield, P. C. ^[2]; Furukawa, Yuji  ^[2]

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1. Ames Laboratory (AMES), Ames, IA (United States)
2. Ames Laboratory (AMES), Ames, IA (United States); Iowa State Univ., Ames, IA (United States)

In this study, ¹³⁹La nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements have been performed to investigate the magnetic properties of the itinerant magnet La₂Ni₇, which shows a series of antiferromagnetic (AFM) phase transitions at T_N1= 61 K, T_N2 = 56 K, and T_N3 = 42 K under zero magnetic field. Two distinct La NMR signals were observed due to the two crystallographically inequivalent La sites in La₂Ni₇ (La1 and La2 in the La₂ Ni₄ and the LaNi₅ subunits of the La₂Ni₇ unit cell, respectively). From the ¹³⁹La NQR spectrum in the AFM state below T_N3, the AFM state was revealed to be a commensurate state where Ni-ordered moments align along the crystalline c axis. Owing to the two different La sites, we were able to estimate the average values of the Ni-ordered moments (0.09 – 0.10_μB/ Ni and 0.17_μB/ Ni around La1 and La2, respectively) from ¹³⁹La NMR spectrum measurements in the AFM state below T_N3, suggesting a nonuniform distribution of the Ni-ordered moments in the AFM state. In contrast, a more uniform distribution of the Ni-ordered moments in the saturated paramagnetic state induced by the application of high magnetic fields is observed. The temperature dependence of the sublattice magnetization measured by the internal magnetic induction at the La2 site in the AFM state was reproduced by a local-moment model better than the self-consistent renormalization (SCR) theory for weak itinerant antiferromagnets. Given the small Ni-ordered moments in the magnetically ordered state, our results suggest that La₂Ni₇ has characteristics of both itinerant nature and localized nature in its magnetism. With this in mind, it is noteworthy that the temperature dependence of nuclear spin-relaxation rates (1/T₁) in the paramagnetic state above T_N1 measured at zero magnetic field can be explained qualitatively by both the SCR theory and the local-moment model.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1994521
• Report Number(s): IS-J-11,130
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 6 Vol. 108; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English