Title of Paper:A Material Showing Colossal Positive and Negative Volumetric Thermal Expansion with Hysteretic Magnetic Transition

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Date of Publication:2017-10-09

Journal:ANGEWANDTE CHEMIE-INTERNATIONAL EDITION

Included Journals:SCIE、EI、PubMed、Scopus

Volume:56

Issue:42

Page Number:13052-13055

ISSN No.:1433-7851

Key Words:charge transfer; hysteresis; magnetic materials; negative thermal expansion; positive thermal expansion

Abstract:It is an ongoing challenge to design and synthesize magnetic materials that undergo colossal thermal expansion and that possess potential applications as microscale or nanoscale actuators with magnetic functionality. A paramagnetic metallocyanate building block was used to construct a cyanide-bridged Fe-Co complex featuring both positive and negative colossal volumetric thermal-expansion behavior. A detailed study revealed that metal-to-metal charge transfer between 180 and 240K induced a volumetric thermal expansion coefficient of 1498 MK-1 accompanied with hysteretic spin transition. Rotation of the magnetic building blocks induced change of pi center dot center dot center dot pi interactions, resulting in a negative volume expansion coefficient of -489 MK-1, and another hysteretic magnetic transition between 300 and 350 K. This work presents a strategy for incorporating both colossal positive and negative volumetric thermal expansion with shape and magnetic memory effects in a material.