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Journal of Physics: Condensed Matter - latest papers

Latest articles for Journal of Physics: Condensed Matter

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  • Role of magnetic ordering on transformation properties of Heusler Ni2MnGa magnetic shape memory alloy
    We pursued a theoretical investigation of the Ni–Mn–Ga Heusler alloy to understand the role of magnetism on the lattice stability and, consequently, the magnetic shape memory (MSM) effect. Two ab initio methods were used for the calculations: the widely used standard density functional theory and the advanced quasiparticle self-consistent GW (QSGW) method. The latter is expected to be more accurate due to the explicit inclusion of electron correlation. The generalized susceptibility calculated by QSGW indicated that the existence of magnetic ordering in the high temperature phase, austenite, is crucial for the formation of the modulated martensites. The ferromagnetic austenite transforms into modulated martensites that can exhibit MSM, but the paramagnetic austenite does not possess this tendency in accordance with experimental observations. In the non-modulated tetragonal martensite (NM), we investigated the role of magnetic ordering on the stability of the lattice and twinning interface. We found that the elastic constants remain unchanged during magnetic moment rotation, confirming the stability of NM in agreement with the notion that it is a ground state. Furthermore, the calculation revealed that the magnetization rotation has a negligible influence on the stability of the twinning interface in NM

  • Machine-learning interatomic potential for BaTiO3: phase transitions, domain walls, and grain boundaries
    A machine learning interatomic potential for BaTiO3 is presented based on the atomic cluster expansion formalism, enabling atomistic simulations of phase transitions, defect structures, and domain walls. Trained on a comprehensive dataset of density-functional theory calculations, the potential effectively captures the sequence of temperature-driven phase transitions from rhombohedral to orthorhombic, tetragonal, and cubic phases. In addition, the effect of pressure on these phase transitions is well described showing a decrease in the transition temperatures with increasing pressure as observed experimentally. The transferability of the potential is exemplified by accurately predicting 180∘ domain-wall structures and the energetics of symmetric tilt grain boundaries in the rhombohedral phase.

  • The influence of ambient high pressure to structural features of barium hexaferrite
    A comprehensive analysis of the magnetic properties, crystal structure and magnetic configuration of the ceramic BaFe12O19, prepared using the sol-gel method, was conducted over the temperature range from 4 K to room temperature. The impact of ambient pressure on the crystal and magnetic structures of ceramic BaFe12O19 has enabled the determination of bulk modulus B0 ∼ 123.8 GPa and its first-order derivative Bp′ ∼ 4.1, as well as the coefficients of linear compressibility of the lattice parameters for the hexagonal unit cell. The results of neutron diffraction collected at pressures ranging from 0.1 GPa to 5 GPa were analyzed in the framework of both centrosymmetric SG P63/mmc (No. 194) and non-centrosymmetric SG P63mc (No. 186). The decrease in the total magnetic moment with an increase in ambient pressure was associated with a weakening of the exchange interaction in the ferrimagnetic structure, owing to a reduction in the bond angles (∠ Fe–O–Fe) of various iron sublattices.

  • Engineering spin-wave spectrum via the magnetization inertia tensor
    Magnetic inertial dynamics has recently been predicted and experimentally demonstrated in two-sublattice ferromagnets such as CoFeB and NiFe permalloy. In this work, we investigate the spin-wave spectrum of such systems by incorporating the complete magnetic inertia tensor. By decomposing the tensor into symmetric and antisymmetric components, we identify isotropic, anisotropic, and chiral contributions to magnetic inertia. Within linear spin-wave theory, we find that the spectrum comprises two precessional and two inertial magnon bands. Remarkably, the upper precessional band intersects the lower inertial band within the Brillouin zone. Both cross-sublattice and chiral components of the inertia tensor act as effective control parameters for tuning these magnonic band structures. Furthermore, we show that the inertial spin-wave spectrum becomes nonreciprocal along propagation directions where the Dzyaloshinskii–Moriya interaction is finite. Strikingly, a similar nonreciprocity can also arise purely from chiral inertia, even in the absence of Dzyaloshinskii–Moriya interaction. Our findings establish magnetic inertia as a new pathway to engineer nonreciprocal magnon transport and ultrafast spintronic functionalities.

  • Spin-wave scattering in square lattices with a linear stacking of anisotropic and antisymmetric bond defects
    We investigate the scattering of spin waves by a linear stack of bond defects in two-dimensional ferromagnetic and antiferromagnetic square lattices. Using a semiclassical approach, we derive exact solutions for the transmission of magnons interacting with defects characterized by exchange anisotropy and Dzyaloshinskii–Moriya interactions. For ferromagnetic systems, we identify a resonance condition that yields omnidirectional transparency when the defect exchange matches the bulk, and momentum-selective transparency when the coupling is reduced. In antiferromagnets, the transmission spectrum exhibits a pronounced dependence on both wavevector components, with full transparency at high-symmetry points and complete reflection along specific momentum-space diagonals. Our results reveal how engineered anisotropic and antisymmetric exchange interactions can be used to control magnon transport, offering guiding principles for the design of spin-wave filters and other magnonic devices.