The magnetocaloric effect of orthorhombic Gd(OH)CO ₃ has been experimentally studied, which exhibits −Δ S _m up to 66.4 J kg ⁻¹ K ⁻¹ (355 mJ cm ⁻³ K ⁻¹ ) for Δ H = 7 T and T = 1.8 K.

KWS-3, which is operated by JCNS, Forschungszentrum Jülich, is a very small angle neutron scattering (VSANS) instrument running on the focussing mirror principle. KWS-3 is designed to bridge the gap between Bonse-Hart and pinhole cameras. Owing to its extended Q range, optimized flux, and good wavelength resolution, KWS-3 has shown good performance and has become scientifically productive to the user community.

We present comprehensive investigations on a pyrochlore antiferromagnet Na${}_3$Co(CO${}_3$)${}_2$Cl. Performed dc magnetization indicates a broad maximum at around 4 K. The field dependence of the peak temperature of this maximum follows the de Almeida–Thouless line, suggesting a spin-glass-like phase transition. The ac susceptibility measurements determine the glassy transition temperature to be 4.5 K and reveal a frequency-independent peak at 17 K. The temperature dependence of the specific heat shows a sharp peak at 1.5 K and a broad hump at around 5 K, which are attributed to a long-range magnetic phase transition and a spin-glass-like freezing process, respectively. The average crystallographic structure of Na${}_3$Co(CO${}_3$)${}_2$Cl has been determined using neutron-powder diffraction. No obvious site disorder has been detected within the experimental resolution. The diffuse neutron scattering with polarization analysis indicates short-range spin correlations characterized by dominating antiferromagnetic coupling between nearest neighbors and weak ferromagnetic coupling between next-nearest neighbors. The long-range magnetic order below 1.5 K is evidenced by the magnetic reflections observed at 50 mK and can be well explained with an all-in–all-out spin configuration. Inelastic neutron scattering of Na${}_3$Co(CO${}_3$)${}_2$Cl exhibits collective magnetic excitations at 3.5 K, suggesting that the spin-glass-like transition temperature $T_{\mathrm{g}}$ $=$ 4.5 K does not correspond to a complete spin-glass freezing as expected in canonical spin glasses. The peak observed in magnetic susceptibility at 17 K is attributed to the onset of an intermediate partially ordered phase transition, qualitatively consistent with the theoretical predictions for pyrochlore antiferromagnets with weak ferromagnetic next-nearest-neighbor interactions.

The magnetic-field-induced assembly of magnetic nanoparticles (NPs) provides a unique and flexible strategy in the design and fabrication of functional nanostructures and devices. We have investigated the field-induced self-assembly of core–shell iron oxide NPs dispersed in toluene by means of small-angle neutron scattering (SANS). The form factor of the core–shell NPs was characterized and analyzed using SANS with polarized neutrons. Large-scale aggregates of iron oxide NPs formed above 0.02 T as indicated by very-small-angle neutron scattering measurements. A three-dimensional long-range ordered superlattice of iron oxide NPs was revealed under the application of a moderate magnetic field. The crystal structure of the superlattice has been identified to be face-centred cubic.

We re-investigate the magnetically frustrated, diamond-lattice-antiferromagnet spinels FeAl${}_{2}$O${}_{4}$ and MnAl${}_{2}$O${}_{4}$ using magnetization measurements and diffuse scattering of polarized neutrons. In FeAl${}_{2}$O${}_{4}$, macroscopic measurements evidence a ``cusp'' in zero field-cooled susceptibility around 13 K. Dynamic magnetic susceptibility and memory effect experiments provide results that do not conform with a canonical spin-glass scenario in this material. Through polarized neutron-scattering studies, absence of long-range magnetic order down to 4 K is confirmed in FeAl${}_{2}$O${}_{4}$. By modeling the powder averaged differential magnetic neutron-scattering cross section, we estimate that the spin-spin correlations in this compound extend up to the third nearest-neighbor shell. The estimated value of the Land\'e $g$ factor points towards orbital contributions from Fe${}^{2+}$. This is also supported by a Curie-Weiss analysis of the magnetic susceptibility. MnAl${}_{2}$O${}_{4}$, on the contrary, undergoes a magnetic phase transition into a long-range ordered state below $$\approx${}$40 K, which is confirmed by macroscopic measurements and polarized neutron diffraction. However, the polarized neutron studies reveal the existence of prominent spin fluctuations co-existing with long-range antiferromagnetic order. The magnetic diffuse intensity suggests a similar short-range order as in FeAl${}_{2}$O${}_{4}$. Results of the present work support the importance of spin-spin correlations in understanding magnetic response of frustrated magnets like $A$-site spinels which have predominant short-range spin correlations reminiscent of the ``spin-liquid'' state.