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Journal Articles

$$mu$$SR studies on copper minerals

Fujihara, Masayoshi; Okabe, Hirotaka*; Koda, Akihiro*

Interactions (Internet), 245(1), p.13_1 - 13_6, 2024/12

https://doi.org/10.1007/s10751-024-01856-7

Quantum states are difficult to observe experimentally. In addition, ideal model materials have not been found for some of the lattice systems in which exotic quantum states are predicted to be realized. Numerous candidates for low-dimensional quantum magnets are hidden in copper minerals, and the number of candidates is increasing every year. We succeeded to synthesize seven copper minerals by imitating the environment where they are discovered and reported their quantum states. The properties of pulsed muons are very suitable for investigating the spin state of artificial copper minerals.

Journal Articles

Spin gap in the weakly interacting quantum spin chain antiferromagnet KCuPO$$_{4}$$$$cdot$$H$$_{2}$$O

Fujihara, Masayoshi; Hagihara, Masato; Morita, Katsuhiro*; Murai, Naoki; Koda, Akihiro*; Okabe, Hirotaka*; Mitsuda, Setsuo*

Physical Review B, 107(5), p.054435_1 - 054435_8, 2023/02

https://doi.org/10.1103/PhysRevB.107.054435
 Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)

The $$S$$ = 1/2 Heisenberg linear chain antiferromagnet is the simplest spin model; nevertheless it serves as a platform for various quantum many-body phenomena. Here, we report the magnetic behavior of a quasi-one-dimensional antiferromagnet KCuPO$$_{4}$$$$cdot$$H$$_{2}$$O. A long-range commensurate antiferromagnetic order with ordered moment 0.31(1) $$mu_{rm{B}}$$ per spin occurs at $$T_{rm{N}}$$ = 11.7(1) K. Above $$T_{rm{N}}$$, the inelastic neutron excitation is characterized by a two spinon continuum. The intrachain interaction $$J$$ and interchain interaction $$|J'|$$ are estimated to be 172 K and 4.25(4) K, respectively; thus the ratio of the $$|J'|$$/$$J$$ = 0.0247(3). At lower energies, below $$T_{rm{N}}$$, a spin gap is observed in the dispersive excitations. These results are consistent with characteristics observed in weakly interacting $$S$$ = 1/2 Heisenberg chain system.

Journal Articles

Birchite Cd$$_{2}$$Cu$$_{2}$$(PO$$_{4}$$)$$_{2}$$SO$$_{4}$$ $$cdot$$ 5H$$_{2}$$O as a model antiferromagnetic spin-1/2 Heisenberg $${it J}$$$$_{1}$$-$${it J}$$$$_{2}$$ chain

Fujihara, Masayoshi; Jeschke, H. O.*; Morita, Katsuhiro*; Kuwai, Tomohiko*; Koda, Akihiro*; Okabe, Hirotaka*; Matsuo, Akira*; Kindo, Koichi*; Mitsuda, Setsuo*

Physical Review Materials (Internet), 6(11), p.114408_1 - 114408_8, 2022/11

https://doi.org/10.1103/PhysRevMaterials.6.114408
 Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)

$${it S}$$ = 1/2 Heisenberg $${it J}$$$$_{1}$$-$${it J}$$$$_{2}$$ chain antiferromagnets have been investigated extensively due to their exotic magnetic states. Here, we report the magnetic behavior of birchite Cd$$_{2}$$Cu$$_{2}$$(PO$$_{4}$$)$$_{2}$$SO$$_{4}$$$$cdot$$5H$$_{2}$$O and its effective spin model. Experimental studies by magnetic susceptibility, magnetization, heat capacity, and $$mu$$SR measurements indicate the absence of long-range order down to 0.4 K. Theoretical studies reveal that birchite is a model compound for the $${it J}$$$$_{1}$$-$${it J}$$$$_{2}$$ antiferromagnetic chain: the intrachain interactions $${it J}$$$$_{1}$$ and $${it J}$$$$_{2}$$ are antiferromagnetic and their magnitude is about 100 times larger than the interchain interactions. The magnitude of $${it J}$$$$_{2}$$ is two to three times larger than that of $${it J}$$$$_{1}$$, thus the spin gap is expected to be only a few percent of that of $${it J}$$$$_{1}$$. The temperature dependence of the specific heat shows a broad peak at about 1 K ($$simeq$$ 0.036 $${it J}$$$$_{1}$$), which suggests the presence of a spin gap.

Journal Articles

Influence of self-irradiation damage on the Pu-based superconductor PuCoGa$$_5$$ probed by muon spin rotation

Oishi, Kazuki; Ito, Takashi; Higemoto, Wataru; Heffner, R. H.

Journal of the Physical Society of Japan, 75(Suppl.), p.53 - 55, 2006/08

PuCoGa$$_5$$ has attracted much interest because it has a high transition temperature $$T_{rm c}$$ ($$simeq$$ 18 K) compared with other 115 systems. According to the previous $$mu$$SR results, temperature dependence of magnetic penetration depth $$lambda$$ in PuCoGa$$_5$$ shows $$T$$-linear behavior, suggesting that the superconducting order parameter of this material may be $$d$$-wave symmetry. In order to elucidate that point, we have measured the magnetic field dependence of $$lambda$$ in this sample by means of $$mu$$SR technique. At our poster presentation, we discuss the symmetry of superconducting order parameter in PuCoGa$$_5$$ in detail.

Journal Articles

Magnetism and superconductivity in CePt$$_3$$Si probed by muon spin relaxation

Higemoto, Wataru; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Koda, Akihiro*; Saha, S. R.*; Oishi, Kazuki; Kadono, Ryosuke*

Journal of the Physical Society of Japan, 75(Suppl.), p.180 - 182, 2006/08

We report on the Magnetism, magnetic penetration depth and the Knight shift in polycrystalline sample of CePt$$_3$$Si by means of muon spin rotation and relaxation method. The appearance of the internal field under the zero magnetic field in whole volume of the specimen, was observed, which indicating clear evidence of antiferromagnetism. The muon Knight shift was measured down to 20mK at 17kOe. Three different frequencies are seen in the muon spin rotation spectra, which depend on the temperature. The symmetry of the superconducting Cooper pair will be discussed.

Journal Articles

New limits on the ordered moments in $$alpha$$-Pu and Ga-stabilized $$delta$$-Pu

Heffner, R. H.; Morris, G. D.*; Fluss, M. J.*; Chung, B.*; MacLaughlin, D. E.*; Shu, L.*; Anderson, J. E.*

Physica B; Condensed Matter, 374-375, p.163 - 166, 2006/03

https://doi.org/10.1016/j.physb.2005.11.042
 Times Cited Count：8 Percentile：38.37(Physics, Condensed Matter)

The $$mu$$SR measurements in pulutonium metals are reported for the first time. The ground-state properties of Pu metal is not understood clearly. We found the upper limits of the ordered moment in $$alpha$$-Pu and $$delta$$-stabilized Pu is $$<10^{-3}mu_B$$ at $$sim$$4K.

Journal Articles

Progress of muon science

Takeda, Tatsuoki; Nagamine, Kanetada*; *; *; Ishida, Katsuhiko*; *; *; Mizumoto, Motoharu

Nihon Genshiryoku Gakkai-Shi, 34(12), p.1098 - 1107, 1992/12

https://doi.org/10.3327/jaesj.34.1098
 Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

no abstracts in English

Oral presentation

$$mu$$SR studies of quantum magnets

Fujihara, Masayoshi

no journal, , 

In recent years, many new copper minerals have been discovered in the volcanic regions of the Kamchatka peninsula. The speaker has found several frustrated low-dimensional quantum magnets in these Kamchatka copper minerals, synthesized them artificially, and investigated their spin states. In this talk, I will introduce the role of the $$mu$$SR method, which is a highly sensitive method for detecting spin dynamics and/or static internal magnetic fields, in these artificial minerals. The importance of complementary use with neutron scattering experiments will also be discussed.

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