Charge order, dielectric response, and local structure of La5/3Sr1/3NiO4 system

Abstract

Charge ordering, dielectric permittivity and local structure of La 5/3 Sr 1/3 NiO 4 system have been explored X-ray charge scattering, complex dielectric impedance spectroscopy, and extended Xray absorption fine structure (EXAFS) measurements, made on the same single crystal sample.The local structure measured by the temperature dependent polarized Ni K-edge EXAFS shows significant distortions in the NiO 2 planes. These local distortions could be reasonable cause of high dielectric permittivity of the title system (ε≈100 at 5K) with the charge ordering in this system being a ferroelectric-like second order transition.

Giant dielectric constant in Nd2NiO4+δ ceramics obtained by spark plasma sintering

“…Upon cooling the temperature down to 150 K, a sharp decrease of dielectric constant is observed, and the dropping temperature increases with increasing the applied frequency. Also, a peak at the corresponding temperature is appeared on the curve for the temperature dependence of tan d. This is a typical of dielectric relaxation, and it is the common feature of giant dielectric constant materials [8][9][10][11][12]. According to the previous work [4,7], the charge ordering temperature of Nd 2 NiO 4.192 ceramics is about 150 K, which is coincided with the temperature of dielectric relaxation.…”

“…The giant dielectric constant should be mainly attributed to the adiabatic small polaronic hopping process, and the polaronic hopping process is closely related to the charge ordering in these materials [8,9]. Recently, the giant dielectric response up to high frequency is also observed in the La 2Àx Sr x NiO 4 (x = 1/8, 1/3) single crystal, and results also show the dielectric response is closely related to the charge stripe ordering [10][11][12]. The giant dielectric response up to high frequency response is the unique characteristic of the nickelates with K 2 NiF 4 structure, and this may allow a potential application of these materials at high frequencies.…”

Enhanced giant dielectric response in Al-substituted La1.75Sr0.25NiO4 ceramics

“…Materials with giant dielectric constant have been of interest since the discovery of CaCu 3 Ti 4 O 12 (CCTO) for their potential application in the microelectronics [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The common feature of these materials is a giant dielectric constant (ε > 10 4 ) over a wide range of temperature, and a sharp decrease of permittivity with increasing the frequency or decreasing the temperature to a critical point without any detectable phase transition.…”

d−dexcitations and charge ordering inLa5/3Sr1<

“…[15][16][17][18][19] In this system the ordering process occurs in a very large temperature range ͑100-240 K͒ and it can be described as a continuous twodimensional ͑2D͒ transition. 20 Exploiting the specific advantages of RIXS, Wakimoto et al 14 have recently investigated the wave number ͑q͒ dependence of the low-energyexcitation spectra of La 5/3 Sr 1/3 NiO 4 . In this paper, we present studies on the temperature dependence of the d-d electronic excitations in La 5/3 Sr 1/3 NiO 4 .…”