Ironbased extended metal atom chains (EMACs) are potentially highspin molecules with axial magnetic anisotropy and thus candidate singlemolecule magnets (SMMs). We herein compare the tetrairon( ii ), halidecapped complexes [Fe 4 (tpda) 3 Cl 2 ] ( 1Cl ) and [Fe 4 (tpda) 3 Br 2 ] ( 1Br ), obtained by reacting iron( ii ) dihalides with [Fe 2 (Mes) 4 ] and N 2 , N 6 di(pyridin2yl)pyridine2,6diamine (H 2 tpda) in toluene, under strictly anhydrous and anaerobic conditions (HMes = mesitylene). Detailed structural, electrochemical and Mössbauer data are presented along with directcurrent (DC) and alternatingcurrent (AC) magnetic characterizations. DC measurements revealed similar static magnetic properties for the two derivatives, with χ M T at room temperature above that for independent spin carriers, but much lower at low temperature. The electronic structure of the iron( ii ) ions in each derivative was explored by ab initio (CASSCFNEVPT2SO) calculations, which showed that the main magnetic axis of all metals is directed close to the axis of the chain. The outer metals, Fe1 and Fe4, have an easyaxis magnetic anisotropy ( D = −11 to −19 cm −1 ,  E / D  = 0.05–0.18), while the internal metals,more »
Inplane uniaxial pressureinduced outofplane antiferromagnetic moment and critical fluctuations in BaFe2As2
Abstract A small inplane external uniaxial pressure has been widely used as an effective method to acquire single domain iron pnictide BaFe 2 As 2 , which exhibits twindomains without uniaxial strain below the tetragonaltoorthorhombic structural (nematic) transition temperature T s . Although it is generally assumed that such a pressure will not affect the intrinsic electronic/magnetic properties of the system, it is known to enhance the antiferromagnetic (AF) ordering temperature T N ( < T s ) and create inplane resistivity anisotropy above T s . Here we use neutron polarization analysis to show that such a strain on BaFe 2 As 2 also induces a static or quasistatic outofplane ( c axis) AF order and its associated critical spin fluctuations near T N / T s . Therefore, uniaxial pressure necessary to detwin single crystals of BaFe 2 As 2 actually rotates the easy axis of the collinear AF order near T N / T s , and such effects due to spinorbit coupling must be taken into account to unveil the intrinsic electronic/magnetic properties of the system.
 Award ID(s):
 1700081
 Publication Date:
 NSFPAR ID:
 10291293
 Journal Name:
 Nature Communications
 Volume:
 11
 Issue:
 1
 ISSN:
 20411723
 Sponsoring Org:
 National Science Foundation
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