The magnetic properties of several quasi two-dimensional Heisenberg layer compounds: A new class of ferromagnetic insulators involving halocuprates

Abstract

Magnetic susceptibility measurements on powdered samples of bis(benzylammonium) tetrachlorocuprate (II), bis(phenethylammonium) tetrachlorocuprate(II), bis(3-phenyl-1-propylammonium) tetrachlorocuprate(II), and bis(benzylammonium) tetrabromocuprate(II) have shown that these four substances order ferromagnetically with Curie temperatures of 8.0±0.5, 9.0±0.2, 7.0±0.5, and 12.3±1.0 K, respectively. Fits of a series expansion for a two-dimensional lattice to the magnetic susceptibility data obtained from powdered samples in the paramagnetic region yielded exchange constants J for the chloride compounds in the range 16.7–18.8 K, and a value of 25.3 K for the bromide compound. For these fits the <g≳ value of 2.14±0.01 determined from EPR measurements was used. Magnetic susceptibility measurements made at 10 Oe on a single crystal of bis(phenethylammonium) CuCl4 at temperatures just below Tc revealed ratios of susceptibilities of 30:7:1 along the c, a, and b axes, respectively, where the b axis is perpendicular to the thin tabular plates. Magnetization measurements on a single crystal sample of this compound showed that the easy axis, the c axis, and the next-preferred axis, the a axis, were saturated above 60 and 200 Oe, respectively, while magnetic fields greater than 1800 Oe were required for saturation along the b axis. Magnetization measurements on a single crystal of bis(benzylammonium) tetrabromocuprate(II) did not reveal any anisotropy within the plane of the plate, where the saturation field was 50 Oe at 4.2 K, while a field of 1800 Oe was required for saturation along the direction perpendicular to the plate. Anisotropy fields derived from the magnetic susceptibility and magnetization data obtained from measurements on single crystals of bis(benzylammonium) tetrachlorocuprate(II) and bis(phenethylammonium) tetrachlorocuptrate(II) cannot be explained by the calculated exchange and dipolar fields, and it is suggested that an additional mechanism contributes to the anisotropy.

Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

“…Theo bserved rise in magnetization as the temperature decreases are characteristics of the temperature dependence of the magnetization of aferromagnetic substance. [45,46] Long-range ferromagnetic orders for the (PED)CuCl 4 and (BED) 2 CuCl 6 are below 13 K. TheC urie temperatures of these two 2D perovskites are similar to that observed on CuCl 4 (C 6 H 5 CH 2 CH 2 NH 3 ) 2 . [47] Thef erromagnetic hysteresis loops for the two hybrid perovskites below the Curie temperature are shown in Figure 5c,d.F or (PED)CuCl 4 ,t he magnetization nearly saturates at avalue of 0.12 emu g À1 in afield of 2000 Oe at 2K.However, (BED) 2 CuCl 6 on the other hand, has strong ferromagnetism.…”

Measurement of the acoustic-to-optical phonon coupling in multicomponent systems

“…The ferromagnetic phase transition at 13 K and the improper ferroelectric phase transition at T C = 340 K have extensively been described in Refs. [17][18][19].…”

Lead-Free MA2CuClxBr4–x Hybrid Perovskites

“…39 2D Cu-based perovskites have been previously studied mainly for their interesting magnetic properties, 39,40 whereby they behave like quasi-2D Heisenberg ferromagnets. 41,42 Recently (EDBE)[CuCl 4 ], where EDBE = 2,2′-(ethylenedioxy)bis(ethylammonium), has been applied as cathode material in Li + ions batteries. 43 Pb-based systems with lower dimensionality have also recently been studied as sensitizers to improve the stability of these materials against moisture, 44 and the 1D system with perovskite-related structure (CH 3 CH 2 NH 3 )PbI 3 was shown to work as sensitizer in solar cells.…”

“…Moreover, the Jahn–Teller distortion introduces elastic semicoordinate bonds in the inorganic planes, which confers higher flexibility to the structure, resulting in an easier interaction even with larger organoammonium cations and offering wider synthetic tunability . 2D Cu-based perovskites have been previously studied mainly for their interesting magnetic properties, , whereby they behave like quasi-2D Heisenberg ferromagnets. , Recently (EDBE)­[CuCl 4 ], where EDBE = 2,2′-(ethylenedioxy)­bis­(ethylammonium), has been applied as cathode material in Li + ions batteries . Pb-based systems with lower dimensionality have also recently been studied as sensitizers to improve the stability of these materials against moisture, and the 1D system with perovskite-related structure (CH 3 CH 2 NH 3 )­PbI 3 was shown to work as sensitizer in solar cells .…”