Ferromagnetic crossover within the ferromagnetic order of UTe

Opletal, P.; Sakai, Hironori; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo

Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03

https://doi.org/10.7566/JPSJ.92.034704

We investigate the physical properties of a single crystal of uranium telluride UTe. We have confirmed that UTe crystallizes in the hexagonal structure with three nonequivalent crystallographic uranium sites. The paramagnetic moments are estimated to be approximately 1 per the uranium site, assuming a uniform moment on all the sites. A ferromagnetic phase transition occurs at = 48 K, where the in-plane magnetization increases sharply, whereas the out of-plane component does not increase significantly. With decreasing temperature further below under field-cooling conditions, the out-of-plane component increases rapidly around T= 26 K. In contrast, the in-plane component hardly changes at T. Specific heat measurement indicates no -type anomaly around T, so this is a cross-over suggesting a reorientation of the ordering moments or successive magnetic ordering on the part of the multiple uranium sites.

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe

Noma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Nakamura, Ai*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

https://doi.org/10.7566/JPSJ.90.073707

Intriguing behavior of UCoRhGe ferromagnets in magnetic field along the axis

Pospil, J.*; Haga, Yoshinori; Miyake, Atsushi*; Kambe, Shinsaku; Tokunaga, Yo; Tokunaga, Masashi*; Yamamoto, Etsuji; Proschek, P.*; Voln, J.*; Sechovsk, V.*

Physical Review B, 102(2), p.024442_1 - 024442_13, 2020/07

https://doi.org/10.1103/PhysRevB.102.024442

Magnetization study on the Ising ferromagnet URhGe with high-precision angle-resolved magnetic field near the hard axis

Nakamura, Shota*; Sakakibara, Toshiro*; Shimizu, Yusei*; Kittaka, Shunichiro*; Kono, Yohei*; Haga, Yoshinori; Pospisil, J.; Yamamoto, Etsuji

Progress in Nuclear Science and Technology (Internet), 5, p.123 - 127, 2018/11

https://doi.org/10.15669/pnst.5.123

Electronic states in EuCu(GeSi) based on the doniach phase diagram

Iha, Wataru*; Yara, Tomoyuki*; Ashitomi, Yosuke*; Kakihana, Masashi*; Takeuchi, Tetsuya*; Honda, Fuminori*; Nakamura, Ai*; Aoki, Dai*; Gochi, Jun*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 87(6), p.064706_1 - 064706_14, 2018/06

https://doi.org/10.7566/JPSJ.87.064706

Experimental observation of temperature and magnetic-field evolution of the 4 states in CeFe revealed by soft X-ray magnetic circular dichroism

Saito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

https://doi.org/10.1103/PhysRevB.96.035151

We revisit the delocalized character of the 4 states of CeFe in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce XAS as well as the Fe XAS and XMCD. This unusual behavior is characterized by the states in a 4 configuration mixed into the ground state. Such extreme sensitivity of the Ce 4 states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.

Electronic structures of ferromagnetic CeAgSb; Soft X-ray absorption, magnetic circular dichroism, and angle-resolved photoemission spectroscopies

Saito, Yuji; Fujiwara, Hidenori*; Yamaguchi, Takashi*; Nakatani, Yasuhiro*; Mori, Takeo*; Fuchimoto, Hiroto*; Kiss, Takayuki*; Yasui, Akira*; Miyawaki, Jun*; Imada, Shin*; et al.

Journal of the Physical Society of Japan, 85(11), p.114713_1 - 114713_7, 2016/11

https://doi.org/10.7566/JPSJ.85.114713

We report on the electronic structures of ferromagnetic CeAgSb using soft X-ray absorption (XAS), magnetic circular dichroism (XMCD), and angle-resolved photoemission (ARPES) spectroscopies. The Ce XAS spectra show very small satellite structures, reflecting a strongly localized character of the Ce 4 electrons. The linear dichroism effects in the Ce XAS spectra demonstrate the ground-state Ce 4 symmetry of , the spatial distribution of which is directed along the -axis. Nevertheless, ARPES spectra at the Ce 3-4 resonance show the momentum dependence of the intensity ratio between Ce 4 and 4 peaks in a part of the Brillouin zone, suggesting the non negligible momentum-dependent hybridization effect between the Ce 4 and the conduction electrons. This is associated with the moderate mass enhancement in CeAgSb.

Electrical and magnetic properties of a single crystal UCuSi

Matsuda, Tatsuma; Haga, Yoshinori; Ikeda, Shugo; Galatanu, A.; Yamamoto, Etsuji; Shishido, Hiroaki*; Yamada, Mineko*; Yamaura, Junichi*; Hedo, Masato*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 74(5), p.1552 - 1556, 2005/05

https://doi.org/10.1143/JPSJ.74.1552

We have succeeded in growing a high-quality single crystal of UCuSi with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCuSi is found to order antiferromagnetically below = 106 K, and follows a successive ferromagnetic ordering at = 100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction (-axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction (-axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes smoothly into a ferromagnetic magnetization curve below = 100 K. The saturation moment is determined as 1.75/U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/Kmol.

Large orbital magnetic moment and its quenching in the itinerant uranium intermetallic compounds UGa (=Ni, Pd, Pt)

Kaneko, Koji; Metoki, Naoto; Bernhoeft, N.*; Lander, G. H.; Ishii, Yoshinobu; Ikeda, Shugo; Tokiwa, Yoshifumi; Haga, Yoshinori; Onuki, Yoshichika

Physical Review B, 68(21), p.214419_1 - 214419_9, 2003/12

https://doi.org/10.1103/PhysRevB.68.214419

The crystal structure, lattice strain due to the antiferromagnetic ordering and magnetic form factor in the itinerant 5 compounds UTGa (T: Ni, Pd, Pt) have been studied by neutron scattering. High-resolution powder diffraction revealed that the tetragonality of the U-Ga layers increases with the ionic radius of the transition metal element T. The observed antiferromagnetic reflections can be well explained with the Nel-type structure for UNiGa, whereas UPtGa has the antiferromagnetic stacking of the ferromagnetically ordered uranium moments in the -plane. The orbital contributions in the magnetic form factor are reduced from the free ion value, especially for UNiGa. This suppression shows a strong correlation with the bulk magnetic susceptibility. The tetragonality of the U-Ga layers is a sensitive measure of the nearest neighbour interaction, the lattice anomaly, and the orbital contribution and suggests that orbital degrees of freedom may play an important role for the magnetic properties in these itinerant 5 antiferromagnets.

Ferromagnetism and giant magnetoresistance in the rare-earth fullerides EuSrC

Ishii, Kenji; Fujiwara, Akihiko*; Suematsu, Hiroyoshi*; Kubozono, Yoshihiro*

Physical Review B, 65(13), p.134431_1 - 134431_6, 2002/03

https://doi.org/10.1103/PhysRevB.65.134431

We have studied crystal structure, magnetism and electric transport properties of a europium fulleride EuC and its Sr-substituted compounds, EuSrC. They have a structure, which is an isostructure of other C ( represents an alkali atom or an alkaline earth atom). Magnetic measurements revealed that magnetic moment is ascribed to the divalent europium atom with = 7/2 spin, and a ferromagnetic transition was observed at = 10 - 14 K. In EuC, we also confirm the ferromagnetic transition by heat capacity measurement. The striking feature in EuSrC is very large negative magnetoresistance at low temperature; the resistivity ratio ( = 9 T)/( = 0 T) reaches almost 10 at 1 K in EuC. Such large magnetoresistance is the manifestation of a strong - interaction between conduction carriers on C and 4 electrons of Eu.