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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

Atomic reconstruction induced by uniaxial stress in MnP

Kozawa, Tatsuya*; Fujihara, Masayoshi; Uchihara, Takeru*; Mitsuda, Setsuo*; Yano, Shinichiro*; Tamatsukuri, Hiromu; Munakata, Koji*; Nakao, Akiko*

Scientific Reports (Internet), 13, p.13750_1 - 13750_8, 2023/08

https://doi.org/10.1038/s41598-023-40806-1
 Times Cited Count：0 Percentile：0(Multidisciplinary Sciences)

In condensed matter physics, pressure is frequently used to modify the stability of both electronic states and atomic arrangements. Under isotropic pressure, the intermetallic compound MnP has recently attracted attention for the interplay between pressure-induced superconductivity and complicated magnetic order in the vicinity. By contrast, we use uniaxial stress, a directional type of pressure, to investigate the effect on the magnetism and crystal structure of this compound. An irreversible magnetisation response induced by uniaxial stress is discovered in MnP at uniaxial stress as low as 0.04 GPa. Neutron diffraction experiments reveal that uniaxial stress forms crystal domains that satisfy pseudo-rotational symmetry unique to the MnP-type structure. The structure of the coexisting domains accounts for the stress-induced magnetism. We term this first discovered phenomenon atomic reconstruction (AR) induced by uniaxial stress. Furthermore, our calculation results provide guidelines on the search for AR candidates. AR allows crystal domain engineering to control anisotropic properties of materials, including dielectricity, elasticity, electrical conduction, magnetism and superconductivity. A wide-ranging exploration of potential AR candidates would ensure that crystal domain engineering yields unconventional methods to design functional multi-domain materials for a wide variety of purposes.

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

Gapless spin liquid in a square-kagome lattice antiferromagnet

Fujihara, Masayoshi*; Morita, Katsuhiro*; Mole, R.*; Mitsuda, Setsuo*; Toyama, Takami*; Yano, Shinichiro*; Yu, D.*; Sota, Shigetoshi*; Kuwai, Tomohiko*; Koda, Akihiro*; et al.

Nature Communications (Internet), 11, p.3429_1 - 3429_7, 2020/07

https://doi.org/10.1038/s41467-020-17235-z
 Times Cited Count：37 Percentile：90.63(Multidisciplinary Sciences)

Oral presentation

Quantum magnetism in Kamchatkan copper minerals

Fujihara, Masayoshi

no journal, , 

Quantum spin states in low-dimensional magnetic materials have been extensively studied because of emergent spin gaps and topological features. Intensive studies of one-dimensional linear spin chain antiferromagnets have succeeded in capturing several quantum spin states, such as the Tomonaga-Luttinger spin liquid state and the Haldane state. However in many cases, the lack of suitable model materials of theoretical models has hindered the observation of exotic quantum spin states. In the study of low-dimensional quantum magnets, minerals are often employed as model materials. For example, azurite and herbertsmithite have been identified as candidates for the diamond chain (1D) and kagome lattice (2D) antiferromagnet, and many experimental studies have been performed. In this presentation, I will present results of comprehensive studies of magnetism in Kamchatkan copper minerals fedotovite and atlasovite.

Oral presentation

Magnetic properties of checkerboard lattice antiferromagnet KCuPO$$_4$$H$$_2$$O

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

no journal, , 

no abstracts in English

Oral presentation

Quantum magnetic properties in the quasi-one-dimensional antiferromagnet Na$$_{2}$$CuSO$$_{4}$$Cl$$_{2}$$

Fujihara, Masayoshi

no journal, , 

no abstracts in English

Oral presentation

Magnetic properties of a rhombic lattice antiferromagnet KCoPO$$_4$$H$$_2$$O

Fujihara, Masayoshi; Hagihara, Masato; Okabe, Hirotaka*; Nakamura, Jumpei*; Koda, Akihiro*; Matsuo, Akira*; Kindo, Koichi*; Munakata, Koji*; Ishikado, Motoyuki*

no journal, , 

no abstracts in English

Oral presentation

Muon spin rotation experiment on antiferromagnetic state of $$beta'$$-(BEDT-TTF)$$_2$$ICl$$_2$$ under high pressure

Takaku, Masaki; Higemoto, Wataru; Sato, Kazuhiko*; Saito, Shota*; Ito, Takashi; Fujihara, Masayoshi

no journal, , 

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.

11 (Records 1-11 displayed on this page)
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