During the HiTempMagMat project we developed and optimised synthesis routes and performed comprehensive, multi‑scale investigations of a number of novel multiferroic and magnetoelectric materials. Using solid‑state reactions, tailored atmosphere treatments and several flux‑growth recipes, we produced phase‑pure polycrystalline samples and high‑quality single crystals for key compounds. Studied systems include MnSb2O4, Ni2ScSbO6, BiCrTeO6, BiMnTeO6, Co3O2BO3, SrFe3O(PO4)3 and BaNi2V2O8. Careful optimisation of stoichiometry, heat‑treatment profiles and growth conditions was critical to obtain samples suitable for detailed magnetic and ferroelectric studies.
Samples were characterised by integrated experimental and theoretical approaches to establish structure–property relationships. High‑resolution synchrotron powder and single‑crystal X‑ray diffraction (ESRF, NSRRC) and EXAFS (Elettra, ESRF) provided precise crystallographic and local‑structure information. Neutron diffraction (ANSTO) and muon‑spin relaxation (μSR, PSI) resolved complex spin textures (helical order, ferrimagnetic order, re‑entrant spin‑glass states) and determined magnetic ground states. Bulk thermodynamic and magnetic measurements (dc/ac magnetization, specific heat) elucidated ordering temperatures and magnetocaloric behaviour. To demonstrate multiferroicity and magnetoelectric coupling we measured ferroelectric polarization, dielectric permittivity, magnetodielectric responses and pyrocurrent. Complementary Raman and terahertz spectroscopy mapped strong spin–phonon coupling, phonon renormalization and low‑energy magnon excitations, revealing how lattice dynamics mediate ME responses. Several compounds also exhibited significant magnetocaloric effects, indicating potential for solid‑state refrigeration. First‑principles DFT calculations supported interpretation of spin structures, frustrated exchange networks and microscopic mechanisms for polarization and magnetoelectric coupling, guiding experiments and clarifying observed phenomena.
Collectively, these coordinated synthesis, experimental and theoretical efforts led to the discovery of multiple new ME/multiferroic materials, some with relatively high transition temperatures, sizable ferroelectric polarization, clear linear or field‑induced ME coupling, and promising magnetocaloric/electrocaloric potential.
