Solid state-refrigerants have generated worldwide interest owing to their growing potential for use in efficient and green cooling devices. Caloric effects could be obtained by manipulating their degrees of freedom such as magnetization, electric polarization and volume using a variable external field. In conventional magnetocaloric refrigeration systems, the magnetocaloric effect is exploited by moving the active material in and out of the magnetic field source. Here we demonstrate that a giant and reversible magnetocaloric effect can be generated simply by rotating the multiferroic TbMn 2 O 5 single crystal around its b axis in a relatively low constant magnetic field applied in the ac plane. For a magnetic field applied along the easy axis a, we report an entropy change of 12.25 J/kg K at about 10 K in a field change of 5 T which is 100 times larger than that found when the field is applied along the hard axis c. When the TbMn 2 O 5 is rotated with the field remaining in the ac plane, the associated adiabatic temperature change reaches minimum values of 8 K and 14 K under 2 T and 5 T, respectively. This giant rotating magnetocaloric effect in TbMn 2 O 5 is caused by the "colossal" anisotropy of the entropy change, the enhancement of the magnetization under relatively moderate magnetic fields and the lower magnitude of specific heat. On the other hand, the application of the coherent rotational model demonstrates that the rotating magnetocaloric effect exhibited by TbMn 2 O 5 does not originate directly from the magnetocrystalline anisotropy. Our results should inspire and open new ways toward the implementation of compact, efficient and embedded magnetocaloric devices for low temperature and space application. Its potential operating temperature range of 2 to 30K makes it a great candidate for the liquefaction of hydrogen.

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The spherically averaged structure function S(|q|) obtained from pulsed neutron powder diffraction contains both elastic and inelastic scattering via an integral over energy. The Fourier transformation of S(|q|) to real space, as is done in the pair density function (PDF) analysis, regularizes the data, i.e. it accentuates the diffuse scattering. We present a technique which enables the extraction of off-center (|q| = 0) phonon information from powder diffraction experiments by comparing the experimental PDF with theoretical calculations based on standard interatomic potentials and the crystal symmetry. This procedure (dynamics from powder diffraction(DPD)) has been successfully implemented for two systems, a simple metal, fcc Ni, and an ionic crystal, CaF2. Although computationally intensive, this data analysis allows for a phonon based modeling of the PDF, and additionally provides off-center phonon information from powder neutron diffraction.61.12. Bt, 61.12.Ld, For a variety of physical questions it is significant to obtain information on off-center phonons in crystals. This is particularly important in complex materials where local effects modify the macroscopic properties, as for example in high temperature superconductors, colossal magnetoresistive materials, ferroelectrics, intermetallic alloys and many more. Until this study the only available method to obtain off-center phonon data has been inelastic neutron scattering, which is intensity limited, hence time consuming, and for detailed studies, relies on the availability of large single crystals (triple axis measurements). Here we show how to obtain similar data from powder neutron diffraction.Historically, the purpose of powder (polycrystalline) neutron diffraction has been the exact determination of the average crystal structure using modern crystallographic analysis techniques like Rietveld refinement, see e. g. [1]. Within this type of refinement only a limited range of the momentum transfer q is necessary. More recently, however, the availability of pulsed sources has made possible the measurement of S(|q|) up to very large values of q. The PDF analysis [2] has made use of this additional information to investigate local atomic deviations from an average crystallographic structure.To model the peak positions in the PDF analysis one calculates interatomic distances from the crystallographic unit cell. The peak shape is commonly fitted to the experimentally obtained PDF, ρ exp (r), using Gaussians. Since the experimental PDF contains additional information from the diffuse scattering, observed differences have been successfully attributed to local structural deformations like e. g. polarons [3]. This type of modeling of the PDF does not take into account the intrinsic peak widths caused by coherent excitations in solids like phonons or spin waves, and how the peak widths are modified by a finite momentum transfer cut-off. Other attempts to relate the measured PDF peak widths to the intrinsic phonon dynamics in a real space approach [4] were not inte...