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Observation of Resonant Quantum Magnetoelectric Eﬀect in a Multiferroic Metal−Organic Framework

来源：admin 发布时间：2016-05-16

In recent years, there has been remarkable interest in the synthesis and investigation of hybrid organic−inorganic materials, such as the metal−organic frameworks (MOFs), largely due to their potential applications in gas storage, catalysis, nonlinear optics, photoluminescence, and solar cells as well as their intriguing magnetic and electric properties for fundamental science study. In particular, MOFs with the ABX3 perovskite-like structure are of great interest because the variable A and B components provide plenty of room for adjusting the physical and chemical properties in a simple crystalline structure. In 2009, Jain et al. reported multiferroic behavior in a family of perovskite MOFs, which stimulated considerable experimental and theoretical eﬀorts to search for new multiferroic materials in hybrid MOFs. Multiferroic materials in which magnetic and electric orders coexist have been the subject of extensive research for more than a decade because of their promise for holding large magnetoelectric (ME) coupling eﬀects, i.e., the mutual control of ferroelectric properties by magnetic fields and magnetism by electric fields.
Compared with inorganic multiferroic materials of transition metal oxides, the ME effects in multiferroic MOFs are very weak and even undetectable because their electric and magnetic orders usually have diﬀerent origins. Only recently did our group first report clear ME effects in the multiferroic state of the perovskite MOF [(CH3)2NH2]Fe(HCOO)3 (Fe-MOF). Moreover, we found that this Fe-MOF exhibits resonant quantum tunneling of magnetization (RQTM) at 2 K, a phenomenon previously only seen in the single-molecule and single-ion quantum magnets. Since the discovery of Mn12 single-molecular magnet, the RQTM has attracted remarkable research interests because of its potential for applications in information storage, quantum computing, and molecular spintronics. To measure the RQTM, sophisticated facilities such as superconducting quantum interference device (SQUID) or synchrotron-based spectroscopic techniques are usually employed to detect the magnetization tunneling.
The simultaneous presence of the RQTM and ME coupling makes this Fe-MOF very interesting and unique. In this communication, we demonstrate that the joint eﬀects of the RQTM and ME coupling give rise to a resonant quantum ME eﬀect at low temperatures. This completely new eﬀect enables an electrical detection of RQTM in a very simple and eﬃcient way.
A resonant quantum magnetoelectric coupling eﬀect has been demonstrated in the multiferroic metal−organic framework of [(CH3)2NH2]Fe(HCOO)3. This material shows a coexistence of a spin-canted antiferromagnetic order and ferroelectricity as well as clear magnetoelectric coupling below TN ≈ 19 K. In addition, a component of single-ion quantum magnets develops below ∼8 K because of an intrinsic magnetic phase separation. The stair-shaped magnetic hysteresis loop at 2 K signals resonant quantum tunneling of magnetization. Meanwhile, the magnetic field dependence of dielectric permittivity exhibits sharp peaks just at the critical tunneling fields, evidencing the occurrence of resonant quantum magnetoelectric coupling eﬀect. This resonant eﬀect enables a simple electrical detection of quantum tunneling of magnetization.