Pressure-modulated magnetism and negative thermal expansion in the HoFe intermetallic compound

Cao, Y.*; Zhou, H.*; Khmelevskyi, S.*; Lin, K.*; Avdeev, M.*; Wang, C.-W.*; Wang, B.*; Hu, F.*; Kato, Kenichi*; Hattori, Takanori; et al.

Chemistry of Materials, 35(8), p.3249 - 3255, 2023/04

https://doi.org/10.1021/acs.chemmater.3c00158

Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in HoFe on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level, which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials.

Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFeGe

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

https://doi.org/10.1103/PhysRevLett.122.217003

From a single-band metal to a high-temperature superconductor via two thermal phase transitions

He, R.-H.*; Hashimoto, Makoto*; Karapetyan, H.*; Koralek, J. D.*; Hinton, J. P.*; Testaud, J. P.*; Nathan, V.*; Yoshida, Yoshiyuki*; Yao, H.*; Tanaka, Kiyohisa*; et al.

Science, 331(6024), p.1579 - 1583, 2011/03

https://doi.org/10.1126/science.1198415

The nature of the pseudogap phase of cuprate high-temperature superconductors is a major unsolved problem in condensed matter physics. We studied the commencement of the pseudogap state at temperature using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally doped Bi2201 crystals. We observed the coincident, abrupt onset at of a particle-hole asymmetric antinodal gap in the electronic spectrum, a Kerr rotation in the reflected light polarization, and a change in the ultrafast relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature (), entangled in an energy-momentum dependent manner with the preexisting pseudogap features, ushering in a ground state with coexisting orders.

Beam commissioning software and database for J-PARC LINAC

Sako, Hiroyuki; Sakaki, Hironao; Shen, G.; Takahashi, Hiroki; Yoshikawa, Hiroshi; Ikeda, Hiroshi*; Allen, C. K.*

Proceedings of International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS '07) (CD-ROM), p.698 - 700, 2007/10

A beam commissioning software system based on a relational database has been developed for J-PARC LINAC. A high level application framework with SAD script interperter, JCE was developed in Java. JCE and XAL developed in SNS has been used to write commissioning applications with functions of device control, online modeling and data analysis. A commissioning database system has been developed a base data source for commissioning tools.