Magnetic-Field-Induced Sign Changes of Thermal Expansion in DyCrO_(4)

The anharmonicity of lattice vibration is mainly responsible for the coefficient of thermal expansion(CTE)of materials.External stimuli,such as magnetic and electric fields,thus cannot effectively change the CTE,much less the sign variation from positive to negative or vice versa.In this study,we report significant magnetic field effects on the CTE of zircon-and scheelite-type DyCrO_(4) prepared at ambient and high pressures,respectively.At zero field,the zircon-type DyCrO_(4) exhibits a negative CTE below the ferromagnetic-order temperature of 23 K.With increasing field up to≥1.0 T,however,the sign of the CTE changes from negative to positive.In the scheelite phase,magnetic field can change the initially positive CTE to be negative with a field up to 2.0 T,and then a reentrant positive CTE is induced by enhanced fields≥3.5 T.Both zircon and scheelite phases exhibit considerable magnetostrictive effects with the absolute values as high as~800 ppm at 2 K and 10 T.The strong spin–lattice coupling is discussed to understand the unprecedented sign changes of the CTE caused by applying magnetic fields.The current DyCrO_(4) provides the first example of field-induced sign change of thermal expansion,opening up a way to readily control the thermal expansion beyond the conventional chemical substitution.

Diagnostic features and therapeutic strategies for malignant paraganglioma in a patient:A case report

BACKGROUND Paragangliomas and extra-adrenal pheochromocytomas are uncommon neuroendocrine tumors with ubiquitous distribution.Malignant paraganglioma is a relatively rare entity.We report the treatment and pathological characteristics of a patient with malignant paraganglioma,and summarize the latest advances in the treatment of malignant paraganglioma based on a literature review.CASE SUMMARY A 45-year-old Chinese woman presented to the hospital due to pain in the waist(right side) and right buttock,and was diagnosed as malignant paraganglioma after the placement of ureteral stent,implantation of ileus catheter,and transvaginal removal of the vaginal mass.After relief of intestinal obstruction,the patient received intravenous chemotherapy and peritoneal perfusion chemotherapy.Although her pelvic mass disease was stable,she developed multiple liver metastases and bone metastases.Due to the development of spinal cord compression,she underwent orthopedic surgery,followed by radiotherapy,and molecular targeted therapy with apatinib,but with poor disease control.CONCLUSION Clinical management of paraganglioma is challenging for endocrinologists and oncologists.Prospective studies are required to develop standardized therapeutic strategies for malignant paragangliomas.

Spin glassy behavior and large exchange bias effect in cubic perovskite Ba0.8Sr0.2FeO3-δ

A single-phase iron oxideBa0.8Sr0.2FeO3-δwith a simple cubic perovskite structure in Pm-3 m symmetry is successfully synthesized by a solid-state reaction method in O2 flow. The oxygen content is determined to be about 2.81, indicating the formation of mixed Fe3+and Fe4+charge states with a disorder fashion. As a result, the compound shows small-polaron conductivity behavior, as well as spin glassy features arising from the competition between the ferromagnetic interaction and the antiferromagnetic interaction. Moreover, the competing interactions also give rise to a remarkable exchange bias effect in Ba0.8 Sr0.2 FeO2.81, providing an opportunity to use it in spin devices.