We performed a systematic study of the temperature- and field-dependence of magnetization and resistivity of Gd2PdSi3, which is a centrosymmetric skyrmion crystal. We show that a phase diagram can be constructed based on the anomalous magnetoresistance with one-to-one correspondence among all the feature, while the DC magnetization behavior is consistent with the reported phase diagram based on AC susceptibility. In addition, the crossover boundary from a paramagnetic state into the field-induced ferromagnetic state is also identified. Our results suggest that the ferromagnetic spin fluctuations above the Néel temperature play a key role in the high sensitivity of the resistivity anomalies to magnetic field, pointing to the rich interplay of different magnetic correlations at zero and finite wave vectors underlying the skyrmion lattice in this frustrated itinerant magnet.

Effective nonmagnetic control of the spin structure is at the forefront of the study for functional quantum materials. This study demonstrates that, by applying an anisotropic strain up to only 0.05%, the metamagnetic transition field of spin–orbit‐coupled Mott insulator Sr2IrO4 can be in situ modulated by almost 300%. Simultaneous measurements of resonant X‐ray scattering and transport reveal that this drastic response originates from the complete strain‐tuning of the transition between the spin‐flop and spin‐flip limits, and is always accompanied by large elastoconductance and magnetoconductance. This enables electrically controllable and electronically detectable metamagnetic switching, despite the antiferromagnetic insulating state. The obtained strain‐magnetic field phase diagram reveals that C4‐symmetry‐breaking anisotropy is introduced by strain via pseudospin‐lattice coupling, directly demonstrating the pseudo‐Jahn–Teller effect of spin–orbit‐coupled complex oxides. The extracted coupling strength is much weaker than the superexchange interactions, yet crucial for the spontaneous symmetry‐breaking, affording the remarkably efficient strain‐control.

We report the observation of a linear magnetoresistance in single crystals and epitaxial thin films of the pyrochlore iridate Bi 2 Ir 2 O 7 . The linear magnetoresistance is positive and isotropic at low temperatures, without any sign of saturation up to 35 T. As temperature increases, the linear field dependence gradually evolves to a quadratic field dependence. The temperature and field dependence of magnetoresistance of Bi 2 Ir 2 O 7 bears strikingly resemblance to the scale invariant magnetoresistance observed in the strange metal phase in high T c cuprates. However, the residual resistivity of Bi 2 Ir 2 O 7 is more than two orders of magnitude higher than the curpates. Our results suggest that the correlation between linear magnetoresistance and quantum fluctuations may exist beyond high temperature superconductors.

While geometrically frustrated quantum magnets host rich exotic spin states with potentials for revolutionary quantum technologies, most of them are necessarily good insulators which are difficult to be integrated with modern electrical circuit. The grand challenge is to electrically detect the emergent fluctuations and excitations by introducing charge carriers that interact with the localized spins without destroying their collective spin states. Here, we show that, by designing a Bi2Ir2O7/Dy2Ti2O7 heterostructure, the breaking of the spin-ice rule in insulating Dy2Ti2O7 leads to a charge response in the conducting Bi2Ir2O7 measured as anomalous magnetoresistance during the field-induced Kagome ice-to-saturated ice transition. The magnetoresistive anomaly also captures the characteristic angular and temperature dependence of this ice-rule-breaking transition, which has been understood as magnetic monopole condensation. These results demonstrate a novel heteroepitaxial approach for electronically probing the transition between exotic insulating spin states, laying out a blueprint for the metallization of frustrated quantum magnets.

Ruddlesden-popper type Srn+1IrnO3n+1 compound is a major focus of condensed matter physics where the subtle balance between electron-electron correlation, spin-orbit interaction and crystal field effect brings a host of emergent phenomena. While it is understandable that a canted antiferromagnetic (AFM) insulating state with an easy-plane anisotropy is developed in Sr2IrO4 as the 2D limit of the series, it is intriguing that bilayer Sr3Ir2O7, with slightly higher effective dimensionality, stabilizes c-axis collinear antiferromagnetism. This also renders the Sr3Ir2O7 as a unique playground to study exotic physics near a critical spin transition point.However, the epitaxial growth of the Sr3Ir2O7 is still a challenging task because of the narrow growth window. In our research, we have studied the thermodynamic process during synthesis of Sr3Ir2O7 thin films. We successfully expanded the synthesis window by mapping out the relation between the thin film sample crystal structure and gas pressure. Our work thus provides a more accessible avenue to stabilize metastable materials.