Studies of 27Al NMR in EuAl4

International Conference on Strongly Correlated Electron Systems 2014

Niki, H.^1 ; Nakamura, S.^1 ; Higa, N.^1 ; Kuroshima, H.^1 ; Toji, T.^1 ; Yogi, M.^1 ; Nakamura, A.^1 ; Hedo, M.^1 ; Nakama, T.^1 ; O'Nuki, Y.^1 ; Harima, H.^2

Department of Physics, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa

903-0213, Japan^1

Graduate School of Science, Kobe University, Nada-ku, Kobe

657-8501, Japan^2

关键词: Antiferromagnetic state;    Curie-Weiss temperature;    Effective magnetic moments;    External magnetic field;    Ferromagnetic state;    Magnetic and electronic properties;    Nuclear relaxation time;    Temperature dependence;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/592/1/012030/pdf
DOI  :  10.1088/1742-6596/592/1/012030

来源: IOP

【 摘 要 】

EuAl4orders antiferromagnetically at TN≈ 16 K with an effective magnetic moment of 8.02 μB. In the paramagnetic phase, the magnetic susceptibility of EuAl4follows the Curie-Weiss law with a positive Curie-Weiss temperature θP+14 K. The antiferromagnetic state is changed into the field induced ferromagnetic state at a critical field Hcof approximately 2 T. In order to microscopically investigate the magnetic and electronic properties in EuAl4, the NMR measurements of EuAl4have been carried out at temperatures between 2 and 300 K, applying an external magnetic field of approximately 6.5 T. The27Al NMR spectra corresponding to Al(I) and Al(II) sites are obtained. From the27Al NMR spectra, the isotropic part Kisoand anisotropic part Kanisoof Knight shift, and nuclear quadrupole frequncy νQare obtained. The Kisoand Kanisoshift to negative side with decreasing temperature due to the RKKY interaction. These temperature dependences follow the Curie-Weiss law with θP+14 K, which is consistent with that of the magnetic susceptibility. From the K-χ plot, the values of the hyperfine fields Hhf-isoand Hhf-anisoare -3.231 and -0.162 kOe/μBfor Al(I) site, and -1.823 and -0.264 kOe/μBfor Al(II) site, respectively. The values of νQof27Al nucleus for Al(I) and Al(II) sites are approximately 0.865 and 0.409 MHz, respectively. The nuclear relaxation time T1of27Al NMR for both sites is almost constant in the paramagnetic phase, while the value of 1/T1is abruptly decreased in the ordered ferromagnetic state.