Magnetic and magnetodielectric coupling anomalies in the Haldane spin-chain system Nd2BaNiO5

Abstract

We report the magnetic, heat-capacity, dielectric and magnetodielectric (MDE) behaviour of a Haldane spin-chain compound containing light rare-earth ion, Nd 2 BaNiO 5 , in detail, as a function of temperature (T) and magnetic field (H) down to 2 K. In addition to the well-known long range antiferromagnetic order setting in at (T N =) 48 K as indicated in dc magnetization (M), we have observed another magnetic transition near 10 K; this transition appears to be of a glassy-type which vanishes with a marginal application of external magnetic field (even H= 100 Oe). There are corresponding anomalies in dielectric constant (ɛ') as well with variation of T. The isothermal M(H) curves at 2 and 5 K reveal the existence of a magnetic-field induced transition around 90 kOe; the isothermal ɛ'(H) also tracks such a metamagnetic transition. These results illustrate the MDE coupling in this compound. Additionally, we observe a strong frequency dependence of a step in ɛ'(T) with this feature appearing around 25-30 K for the lowest frequency of 1 kHz, far below T N . This is attributed to interplay between crystal-field effect and exchange interaction between Nd and Ni, which establishes the sensitivity of dielectric measurements to detect such effects. Interestingly enough, the observed dispersions of the ɛ'(T) curves is essentially H-independent in the entire Trange of measurement, despite the existence of MDE coupling, which is in sharp contrast with other heavy rare-earth members in this series.

Magnetoelectric memory in reentrant frozen state and considerable ferroelectricity in the multiferroic spin-chain compound Sm2BaNiO5

“…These are the manifestations of memory effect in the relaxation dynamics. All the above experiments clearly show the spin-glass-like behavior below 8 K, which is consistent with that observed low-T behavior of R 2 BaNiO 5 compounds [18,19,30].…”

“…The intrachain exchange interaction is governed by [24][25][26][27][28]. The multiglass response has been reported in these spin-chain compounds [18,19]. Multiferroic order with a significant magnetoelectric coupling was also reported in a few other spin-chain compounds [28][29][30][31].…”

“…Compared to the SG, glassy dynamics involving electric dipole is rare and not well understood due to insufficient studies [5][6][7][8]. Recently, the multiglass scenario has been proposed in a few oxides and provided a new paradigm of glassiness in the dynamics of electric dipole [9][10][11][12][13][14][15][16][17][18][19][20]. In a majority of the cases glassiness in the electric dipole was proposed from the non-Arrhenius frequency response of freezing temperature.…”

Extraordinarily large intrinsic magnetodielectric coupling of the Tb member within the Haldane spin-chain family R2BaNiO5

“…25] 31]. In sharp contrast to this behavior of Tb compound, we find that the value does not even exceed a few percent for other R members, e.g., Nd, Gd, Dy and Er members [7,[19][20][21][22][23]. The fact that the Tb member alone stands out in this respect rules out any direct role of the Haldane spin-chain.…”

High-temperature ferroelectric order and magnetoelectric coupling driven by the magnetic field cooling effect in R2BaCuO5(R=Er,Dy,Sm)<

“…Recently, the spin-chain compounds R 2 BaNiO 5 [26][27][28][29][30][31] and R 2 BaCoO 5 [32] attract special attention in multiferroics, proposing different origins behind the occurrence of ferroelectric order. In this study, we also observe the ferroelectric order in the unexplored R 2 BaCuO 5 (R = Er, Dy, Sm) series.…”