Magnetic behavior of the low-dimensional compounds Ba2Cu3O4Cl2 and Ba3Cu2O4Cl2

Abstract

Orthorhombic Ba3Cu2O4Cl2 contains folded Cu2O4 chains along the crystallographic a direction with two different Cu sites. In single crystals of this compound the magnetization measured for a field applied parallel to the a axis shows a spin-flop transition at a threshold field of 2.6 T for temperatures below TN≈20 K. Above TN a Curie–Weiss behavior is found with a paramagnetic moment of 2.0 μB per Cu atom. Parallel to the b or c axis the magnetization increases linearly with the field strength, and no metamagnetic transition was detected for these directions. It is concluded that Ba3Cu2O4Cl2 has localized magnetic moments which, at low temperatures, order antiferromagnetically parallel to the a axis. The bulklike magnetic behavior of this compound is probably caused by a strong coupling between the Cu2O4 chains. Tetragonal Ba2Cu3O4Cl2 is built up of Cu3O4 planes, also with two types of copper atoms (CuA,CuB). Its magnetization increases nearly linearly with the field. Below TNA=337 K single-crystalline Ba2Cu3O4Cl2 shows a spontaneous magnetization and ferromagnetic hysteresis for fields applied parallel to the tetragonal [100] or [110] directions. For T<TNB≈33 K, the coercive field is more than one order of magnitude larger compared to that measured in the temperature range TNB<T<TNA. The spontaneous magnetization observed in TNB<T<TNA may be attributed to weak ferromagnetism of the Dzyaloshinsky–Moriya type. The behavior of Ba2Cu3O4Cl2 at lower temperatures, T⩽TNB, is not yet understood.

Magnetization jump in theXXZchain with next-nearest-neighbor exchange

“…This phenomenon called metamagnetic transition was observed for example in TmSe [15], Fe x Mn 1−x TiO 3 [16], Tb 1−x Sc x Mn 2 [17], and the quasi one-dimensional compound Ba 3 Cu 2 O 4 Cl 2 [18]. Previous studies of metamagnetism in the model were restricted to ∆ 1 = ∆ 2 = ∆ [9,11].…”

Spin-orbit interaction induced anisotropic property in interacting quantum wires

“…On the contrary, as the strength of the RSOI decreases for a given strength of the DSOI, the CDW phase region expands, and the ground state of the system becomes the CDW eventually. When δv > δv σ , i.e., in the region below the dotted line, the ground state is the so-called MM phase, which was earlier observed in the Q1 D systems, e.g., Ba 3 Cu 2 O 4 Cl 2 [24], and attributed to the next-nearest-neighbor coupling in the XXZ model [25]. By tuning the parameters properly, the ground state of the system exhibits the crossovers among the SDW, CDW, SS, and MM.…”

Weak antiferromagnetism due to Dzyaloshinskii-Moriya interaction inBa3Cu2OYushankhai1, Wolf2, Müller3 et al. 2000Phys. Rev. BSelf Cite8020View full textAdd to dashboardCite

“…40 K, respectively. [4][5][6][7]18 Below T N,I a small spontaneous magnetization, M 0 , within the basal plane of the tetragonal lattice has been reported.…”

“…Due to the typical Cu 2+ (3d 9 ) states the compound is an insulator. It was found to behave like a classical antiferromagnet with a Néel temperature T N of about 20 K. 7 Below T N and for applied magnetic fields H a parallel to the a-axis this compound shows a spin-flop transition at µ 0 H a ≈ 2.6T. 7 Thus, the 'easy axis' of the antiferromagnetically ordered moments turns out to be the a-axis.…”

“…No weak ferromagnetism has been observed. 7 Preliminary group theoretical analysis showed 19 that in Ba 3 Cu 2 O 4 Cl 2 weak ferromagnetism is forbidden while weak antiferromagnetism cannot be excluded.…”