Magnetic Phase Separation in the Oxypnictide Sr2Cr1.85 Mn1.15As2O2

The authors thank the U.K. Science and Technology Facilities Council (STFC) for provision of neutron beamtime at the ILL under the experiment code 5-31-2665. Data are available from ILL at DOI:10.5291/ILL-DATA.5-31-2665.Peer reviewedPublisher PD

Novel method of healing the fibre reinforced thermoplastic composite: a potential model for offshore applications.

Continuous fibre reinforced thermoplastic composites are increasingly finding their use as engineering materials in many industries due to the excellent fire, smoke and toxicity performance. However, the composite component produced using automated continuous fibre reinforced thermoplastic tapes laying machine are susceptible to sudden failure emanating from microscale cracks. This study demonstrates the healing potential of a layered Glass Fibre Reinforced Polymer (GFRP) composite consisting of alternative layers of GFRP and a magnetic polyamide-6 (PA-6) nanocomposite (PNC) film. The self-healing process is presented in three steps, viz. (i) polymer nanocomposite synthesis, (ii) preparation of the layered GFRP layered composite sample and (iii) self-healing and testing of GFRP layered composite sample. Firstly, the multilayer dog bone sample consisting of a magnetic polymer nanocomposite (PNC) film sandwiched between thermoplastic unidirectional GFRP tapes are prepared. Healing is triggered by exposing the damaged multilayer sample to microwave causing selective heating of nanocomposite film and its subsequent melting. The healing process completes when liquid polymer fills the micro-crack in the multilayer tape through capillary action and solidifies upon cooling. The healing yields 84% of the undamaged tensile strength recovery. Results demonstrate the potential application of an autonomous self-healing method for thermoplastic composite used in the offshore environment

Electronic Phase Separation in the Hexagonal Perovskite Ba3SrMo2O9

ACKNOWLEDGEMENTS We thank the Carnegie Trust for the Universities of Scotland for a PhD Scholarship for S.S. We acknowledge STFC-GB for provision of beamtime at the ILL. We also thank Dr. Mark Senn (University of Warwick) for useful discussions.Peer reviewedPostprin

Tuneable magnetic nanocomposites for remote self-healing.

When polymer composites containing magnetic nanoparticles (MNPs) are exposed to an alternating magnetic field, heat is generated to melt the surrounding polymer locally, partially filling voids across any cracks or deformities. Such materials are of interest for structural applications; however, structural polymers with high melting temperatures pose the challenge of generating high localised temperatures enabling self-healing. A method to prepare a multiferroic-Polyamide 6 (PA6) nanocomposite with tuneable magnetocaloric properties is reported. Tunability arises from varying the MNP material (and any coating, its dispersion, and agglomerate sizes in the nanocomposite). The superparamagnetic MNPs (SMNPs) and iron oxide MNPs with and without surface functionalization were dispersed into PA6 through in situ polymerization, and their magnetic properties were compared. Furthermore, computer simulations were used to quantify the dispersion state of MNPs and assess the influence of the interaction radius on the magnetic response of the self-healable magnetic nanoparticle polymer (SHMNP) composite. It was shown that maintaining the low interaction radius through the dispersion of the low coercivity MNPs could allow tuning of the bulk magnetocaloric properties of the resulting mesostructures. An in-situ polymerization method improved the dispersion and reduced the maximum interaction radius value from ca. 806 to 371 nm and increased the magnetic response for the silica-coated SMNP composite. This sample displayed ca. three orders of magnitude enhancement for magnetic saturation compared to the unfunctionalized Fe3O4 MNP composite

Anomalous evolution of the magnetocaloric effect in dilute triangular Ising antiferromagnets Tb1−xYx(HCO2)3Tb_{1-x}Y_{x}(HCO_{2})_{3}

We investigate the effects of diamagnetic doping in the solid-solution series $Tb_{1-x}Y_{x}(HCO_{2})_{3}$, in which the parent $Tb(HCO_{2})_{3}$ phase has previously been shown to host a combination of frustrated and quasi-1D physics, giving rise to a triangular Ising antiferromagnetic ground state that lacks long range 3D order. Heat capacity measurements show three key features: (i) a low temperature Schottky anomaly is observed, which is constant as a function of x; (ii) the transition temperature and associated entropy change are both surprisingly robust to diamagnetic doping; and (iii) an additional contribution at T < 0.4 K appears with increasing x. The origin of this unusual behaviour is rationalised in terms of the fragmentation of quasi-1D spin chains by the diamagnetic $Y^{3+}$ dopant. Magnetocaloric measurements show a nonlinear dependence on x. The mass-weighted magnetocaloric entropy decreases across the series from the promising values in $Tb(HCO_{2})_{3}$; however, the magnetocaloric entropy per magnetic $Tb^{3+}$ ion first decreases then increases with increasing x. Our results establish $Tb_{1-x}Y_{x}(HCO_{2})_{3}$ as a model system in which to explore the functional ramifications of dilution in a low-dimensional magnet.Comment: 11 pages and 5 figures excluding supplementary informatio

Localised spin dimers and structural distortions in the hexagonal perovskite Ba3CaMo2O9

Open Access under the ACS OA Agreement Acknowledgments JWe thank the Carnegie Trust for the Universities of Scotland for a PhD Scholarship for S.S. and the U.K. Science and Technology Facilities Council (STFC) for provision of neutron beamtime at the ILL under the experiment code 5-31-2703. Data are available from ILL at DOI: 10.5291/ILL-DATA.5-31-2703.Peer reviewedPublisher PD

The Electronic and Magnetic Properties of Cation Ordered Sr2Mn2.23Cr0.77As2O2

ACKNOWLEDGMENT This research is supported by the EPSRC (research grant EP/L002493/1). We also acknowledge the UK Science and Technology Facilities Council (STFC) for provision of beam time at the ILL.Peer reviewedPostprin

Role of interface in optimisation of polyamide-6/Fe3O4 nanocomposite properties suitable for induction heating.

Induction heating of magnetic nanoparticles (MNPs) and localised melting of the surrounding high temperature engineering polymer matrix by generating microscopic or macroscopic eddy currents during magnetisation of a polymer nanocomposite (PMC) is crucial for realising induction heating-aided structural bonding. However, the polymer heating should be homogeneous and efficient to avoid local pyrolysis of the polymer matrix, which results in degraded mechanical properties, or requiring a large coil for generating a high frequency magnetic field. Increasing the interfacial area by homogeneously dispersing the MNPs in the polymer matrix provides many microscopic eddy currents to dissipate the power through magnetisation and polarisation, leading to micro eddy current induced uniform heating of the PMC. However, the application of a hydrophobic coating on MNPs to aid dispersion can perturb the generation of eddy currents and affect the crystallinity and size of the crystallites responsible for the mechanical properties. In this work, the dielectric and magnetic properties, as well as the degree/size of crystallinity of a PMC containing oleic acid (OA) (22 and 55 w/w%) and silica coated (Stöber and reverse emulsion method) Fe3O4 MNPs were measured to evaluate the effect of the interfacial coating and its chemistry. The correlation between the measured properties and dispersion state of the MNPs was established to demonstrate the comprehensive effects of interfacial coating on the PMC and this is a unique method to select a suitable PMC for induction aided structural bonding applications. The results showed that the lower amount of OA (22 w/w%) helped achieve the best dispersion to reduce the crystallinity size and increase degree of crystallinity, and to give the best candidate for achieving mechanical properties of the bonded carbon fibre reinforced polymer (CFRP). Moreover, the low concentration of OA helped achieve high polarisation for dielectric heating as well as eddy current formation due to the relatively high magnetic saturation. The silica coating proportionally reduced the magnetic response and electric polarisation of the PMC, which could affect its eddy current generation that is responsible for induction heating