Dazhi Hu

Evolution of the intrinsic electronic phase separation in La 0.6 Er 0.1 Sr 0.3 MnO 3 perovskite

Magnetic and electronic transport properties of perovskite manganite La0.6Er0.1Sr0.3MnO3 have been thoroughly examined through the measurements of magnetization, electron paramagnetic resonance(EPR), and resistivity. It was found that the substitution of Er3+ for La3+ ions introduced the chemical disorder and additional strain in this sample. An extra resonance signal occurred in EPR spectra at high temperatures well above TC gives a strong evidence of electronic phase separation(EPS). The analysis of resistivity enable us to identify the polaronic transport mechanism in the paramagnetic region. At low temperature, a new ferromagnetic interaction generates in the microdomains of Er3+-disorder causing the second increase of magnetization. However, the new ferromagnetic interaction does not improve but decreases electronic transport due to the enhancement of interface resistance among neighboring domains. In view of a really wide temperature region for the EPS existence, this sample provides an ideal platform to uncover the evolution law of different magnetic structures in perovskite manganites.

Magnetic entropy change and accurate determination of Curie temperature in single-crystalline helimagnet FeGe

Cubic helimagnet FeGe has emerged as a class of skyrmion materials near room temperature that may impact future information technology. Experimentally identifying the detailed properties of skyrmion materials enables their practical application acceleratedly. Here we study the magnetic entropy change (MEC) of single-crystalline FeGe in its precursor region and clarify its close relation to the critical exponents of a second-order phase transition in this area. The maximum MEC is found to be 2.86 J/kg K for a 7.0 T magnetic-field change smaller than that of common magnetocaloric materials indicating the multiplicity and complexity of the magnetic structure phases in the precursor region. This result also implies that the competition among the multimagnetic phases can partly counteract the magnetic-field–driven force and establishes a stable balance. Based on the obtained MEC and the critical exponents, the exact Curie temperature of single-crystalline FeGe under zero magnetic field is confirmed to be 279.1 K, higher than the previously reported 278.2 K. This finding paves the way for reconstruction of the FeGe phase diagram in the precursor region.

Magnetic field-driven 3D-Heisenberg-like phase transition in single crystalline helimagnet FeGe

Significant microscopic information about fundamental magnetic interactions of magnetic materials is probed via the critical behavior of paramagnetic-ferromagnetic phase transition. In this work, we demonstrate that the critical behavior of cubic single crystalline FeGe belongs to the isotropic 3D-Heisenberg universality class by measuring the field dependence of magnetic entropy change. The above transition is one of the magnetic field-driven phase transitions but has a feature of the crossover from first- to second-order phase transition. A phenomenological model based on the evolution of magnetic skyrmions was proposed to qualitatively understand the phase transition.

Suppression of ferromagnetism and metal-like conductivity in lightly Fe-doped SrRuO3

The magnetic and electronic transport properties of the lightly doped SrRu1-x Fex O3 (x ≤ 0.15) have been studied. All the samples show a paramagnetic-ferromagnetic phase transition and hysteresis effect. With the increase of Fe, the temperature of magnetic phase transition decreases but coercive field increases indicting the existence of antiferromagnetic interaction and magnetic-crystalline anisotropy. In low temperature, all the doping samples exhibit an insulating behavior while metal feature appears only at x ≤ 0.10 samples. The induced disorder suppresses the itinerant property of Ru 4d electron due to Fe random occupation. As a result, the ferromagnetism is weakened and metal-insulator transition is suppressed.

Short-range antiferromagnetic correlations and large magnetic entropy change in (La0.5Pr0.5)0.67Ca0.33MnO3

We report a detailed study of magnetic properties in manganite (La0.5Pr0.5)0.67Ca0.33MnO3. In contrast to the usual beliefs, it shows an abnormal upturn deviation from the Curie–Weiss law on the inverse susceptibility curve. Such a non-Griffiths-like phase is further confirmed from the inverse double integrated intensities of electron paramagnetic resonance spectrum. Because La

CARRIER-LATTICE RELAXATION FOR BROADENING EPR LINEWIDTH IN Nd0.55Sr0.45MnO3

^{3+}

Magnetic and magnetocaloric properties of nanocrystalline La0.5Sr0.5MnO3

3+ ions are substituted by Pr