The applicability of recently discovered materials with extremely high (“colossal”) dielectric constants, required for future electronics, suffers from the fact that their dielectric constant ${\epsilon }^{\prime }$ only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of a charge-ordered nickelate, ${\text{La}}_{15/8}{\text{Sr}}_{1/8}{\text{NiO}}_4$ , surpass those of other materials. Especially, ${\epsilon }^{\prime }$ retains its colossal magnitude of $>10000$ well into the gigahertz range.

Going to Ground: Frustrated systems, in which the geometry of the crystal lattice stands in the way of achieving an energetic minimum on all lattice sites simultaneously, have the potential to remain disordered down to the lowest temperatures. Numerous experimental efforts to find a material with a truly fluctuating ground state have failed because ordering often sets in at a finite temperature owing to symmetry breaking. Nakatsuji et al. (p. 559 ; see the Perspective by Balents ) identify the compound Ba ₃ CuSb ₂ O ₉ as a promising candidate for this state; the Cu-Sb dipoles reside on a hexagonal structure, forming fluctuating spin singlets. Multiple lines of evidence suggest that the material does not order down to the millikelvin temperature range, remaining magnetically isotropic.

The magnetic properties of ${\mathrm{YVO}}_3$ single crystals have been studied in the temperature range from 350 to 4.2 K and in magnetic fields up to 7 T. It is found that in an applied field less than 4 kOe remarkable magnetization reversals occur at two distinct temperatures: an abrupt switch at $T_s=77\mathrm{}$ K associated with a first-order structure phase transition and a gradual reversal at $T^{*}\approx 95$ K without a structural anomaly. Most interestingly, the magnetization always switches to the opposite direction if the crystal is cooled or warmed through $T_s$ and $T^{*}$ in a field less than ∼500 Oe. In higher magnetic fields the magnetization does not change sign but has a minimum at $T^{*}$ and a sudden change at $T_s.$ A possible mechanism for the observed peculiar magnetic behavior is discussed, related to the competition of the single-ion magnetic anisotropy and the antisymmetric Dzyaloshinsky-Moriya interaction accompanied by a change of orbital ordering.