arXiv subjects

Jian-Ping Zhou

Publications and source records attributed to Jian-Ping Zhou.

3 recordsLinked to original sources

arXiv2026

Dielectric, magnetic, and magnetodielectric behaviors of BaFe12O19 hexaferrite modulated by Mn and Ti substitutions

We prepared Mn- and Ti mono-doped and co-doped BaFe12O19 hexaferrites via solid-state reaction to investigate the interplay between magnetic and dielectric properties. Mn2+ ions preferentially occupy the 4f2 and 2b sites, while Ti4+ ions mainly substitute the Fe3+ ions at 4f1 and 12k sites as revealed by the Raman spectroscopy and formation energy. Pure BaFe12O19 exhibits ferrimagnetism. The hexaferrites related to Ti doping have noncollinear longitudinal conical spin order at low temperatures, where BaFe6Mn3Ti3O19 retains this spin order up to room temperature. Ti4+ substitution at 4f1 and 12k sites plays a pivotal role in stabilizing the noncollinear conical spin order through adjusting the superexchange interactions and reducing the uniaxial magnetocrystalline anisotropy along the c-axis. The magnetic response exhibits two distinct transition temperatures because Ti4+ ions interrupt the magnetic superexchange interactions with two inequivalent exchange integrals. Pure BaFe12O19 presents a quantum paraelectric behavior at low temperatures, which is disrupted by Mn-Ti co-doping due to the decoupling of electric dipoles within the triangular bipyramid. Electron hopping and polaronic effects dominate the dielectric response at 10-50 K, while Maxwell-Wagner interfacial polarization and electron hopping contribute to dielectric dispersion at higher temperatures. The negative MD effect of pure BaFe12O19 and BaFe6Mn3Ti3O19 at 10 K originates from spin-phonon coupling and electric polarization induced by noncollinear spin order under magnetic field, respectively. The Mn-Ti co-doped samples achieve relatively higher MD responses at low magnetic fields. In higher temperatures, the MD effect arises mainly from the magnetic field modulation of the electron hopping with non-intrinsic interfacial polarization.

cond-mat.mtrl-sci↗

arXiv2026

Different dielectric, magnetic, and magnetodielectric mechanisms in M-type BaFe12O19 hexaferrite regulated by doping Ga3+ and In3+ cations

We systematically investigated the magnetic, dielectric, and MD properties of BaFe12-xMexO19 ceramics prepared by a solid-state reaction method. The Ga3+ cations with a smaller radius preferentially substitute the Fe3+ ions in FeO6 octahedra while the In3+ cations with a larger radius tend to replace the Fe3+ ions in FeO5 bipyramids of R blocks, inducing different physical characteristics. The pure BaFe12O19 and Ga-doped samples show ferrimagnetism in the temperature range from 10 K to 300 K. The In-doped samples exhibit a transition from non-collinear magnetism to collinear ferrimagnetism. The dielectric decrease of pure BaFe12O19 at around 10-175 K is attributed to the quantum paraelectric state, and the shoulder peaks of loss at about 140-200 K are from electron hopping. The dipole glass state is responsible for the dielectric peak of Ga-doped samples at around 20-40 K. The dielectric increase and plateau of In-doped samples are mainly ascribed to the electron hopping at low temperatures. Their dielectric properties at high temperatures are all attributed to the interfacial polarization caused by the Maxwell-Wagner effect. The MD effect also has different origins for the various samples at low temperatures. For the pure BaFe12O19, the negative MD effect at extremely low temperatures and the positive MD effect after warming are ascribed to spin-phonon coupling and field-dependent electron hopping, respectively. The positive MD effect in Ga-doped hexaferrites results from the field-dependent electric dipoles inside FeO5 bipyramids. For the In-doped samples, the negative MD effect and subsequent transformation to the positive MD effect originate from the field-dependent non-collinear spin ordering and electron hopping, respectively. The MD effect at high temperatures is attributed to the combination of magnetoresistance and Maxwell-Wagner effects.

cond-mat.mtrl-sci↗

arXiv2026

PhysLLM: Harnessing Large Language Models for Cross-Modal Remote Physiological Sensing

Remote photoplethysmography (rPPG) enables non-contact physiological measurement but remains highly susceptible to illumination changes, motion artifacts, and limited temporal modeling. Large Language Models (LLMs) excel at capturing long-range dependencies, offering a potential solution but struggle with the continuous, noise-sensitive nature of rPPG signals due to their text-centric design. To bridge this gap, we introduce the PhysLLM, a collaborative optimization framework that synergizes LLMs with domain-specific rPPG components. Specifically, the Text Prototype Guidance (TPG) strategy is proposed to establish cross-modal alignment by projecting hemodynamic features into LLM-interpretable semantic space, effectively bridging the representational gap between physiological signals and linguistic tokens. Besides, a novel Dual-Domain Stationary (DDS) Algorithm is proposed for resolving signal instability through adaptive time-frequency domain feature re-weighting. Finally, rPPG task-specific cues systematically inject physiological priors through physiological statistics, environmental contextual answering, and task description, leveraging cross-modal learning to integrate both visual and textual information, enabling dynamic adaptation to challenging scenarios like variable illumination and subject movements. Evaluation on four benchmark datasets, PhysLLM achieves state-of-the-art accuracy and robustness, demonstrating superior generalization across lighting variations and motion scenarios. The source code is available at https://github.com/Alex036225/PhysLLM.

cs.CV↗