Temperature dependence of field-induced spin reorientation in GdFeO3

Transient Magnetoelectric Coupling Induced by the Dynamic Intertwinement between Exchange Striction and Compensation in GdFeO3

In this study, we investigate the dynamic magnetoelectric (ME) coupling behaviors of GdFeO3 under pulsed magnetic fields. When a magnetic field is applied along the c-axis, and the temperature is near the compensation temperature (Tcomp = 3.5 K), we observe a subtle transition involving the reversal of Fe3+ moments at approximately 0.8 T in magnetization (M) measurements. This transition induces a corresponding jump in electrical polarization (P), which is not present in the static field measurements. The dynamic intertwining between M and P signifies a competition between antiferromagnetic (AFM) coupling between Gd3+ and Fe3+ moments and their Zeeman energies. The robust AFM coupling leads to the reversal of Fe3+ moments near Tcomp, triggering the abrupt change in P. Based on the exchange striction mechanism in the ferrimagnetic GdFeO3, we propose the possibility of achieving highly magnetic field sensitive ME coupling near the compensation temperature in ferrimagnetic multiferroic orthoferrites.

Limits of Solid Solution and Evolution of Crystal Morphology in (La1-xREx)FeO3 Perovskites by Low Temperature Hydrothermal Crystallization

The crystallization of a new series of A-site substituted lanthanum ferrite materials (La_1-xRE_x)FeO₃ was explored by the hydrothermal method at 240 °C, for rare earth (RE) = Nd, Sm, Gd, Ho, Er, Yb, and Y, with 0 ≤ x ≤ 1. The effect of elemental substitution on the morphological, structural, and magnetic properties of the materials was studied using high-resolution powder X-ray diffraction, energy dispersive spectroscopy (EDS) on the scanning electron microscope, Raman spectroscopy, and SQUID magnetometry. If the radius of the La³⁺ and the substituent ions is similar, such as for Nd³⁺, Sm³⁺, and Gd³⁺, homogeneous solid solutions are formed, with the orthorhombic GdFeO₃-type structure, and a continuous evolution of Raman spectra with composition and distinct magnetic behavior from the end members. When the radius difference between substituents and La³⁺ is large, such as for Ho³⁺, Er³⁺, Yb³⁺, and Y³⁺, then instead of forming solid solutions, crystallization in separate phases is found. However, low levels of element mixing are found and intergrowths of segregated regions give composite particles. In this case, the Raman spectra and magnetic behavior are characteristic of mixtures of phases, while EDS shows distinctive elemental segregation. A-site replacement induces an evolution in the crystallite shape with an increasing amount of substituent ions and this is most evident for RE = Y from cube-shaped crystals seen for LaFeO₃ to multipodal crystals for (La_1-xY_x)FeO₃, providing evidence for a phase-separation-driven evolution of morphology.

Tailoring of magnetic orderings in Fe substituted GdMnO3 bulk samples towards room temperature

The evolution of various magnetic ordering has been studied for the orthorhombic perovskite GdMn_1-x Fe _x O₃ (0  ⩽  x  ⩽  0.7) system to obtain its comprehensive magnetic phase diagram. We observed that the substitution of Fe in GdMnO₃ increases the antiferromagnetic Neel temperature (T _N) from 40 K to above 400 K and importantly induces a spin-reorientation transition (T _SR) for x  ⩾  0.4. These transitions are close to room temperature at x  =  0.5 and then gradually separated at a higher x value. The static orbital ordering induced by the Jahn-Teller distortion seems to play an important role in changing the T _N. The variations of spin-reorientation ordering along with the competition between the magnetic orderings as a function of the composition were discussed with respect to antisymmetric exchange interactions and Mn³⁺ single-ion anisotropy in detail. In addition, the correlation between structural and magnetic properties suggests that the subtle structural change at composition x  =  0.4 may affect the magnetic ordering. The observed tunable T _SR and T _N in GdMn_1-x Fe _x O₃ could add a practical value for these compositions in fields like spintronics and sensors.

Coexistence of weak ferromagnetism and ferroelectricity in the high pressure LiNbO3-type phase of FeTiO3

We report the magnetic and electrical characteristics of polycrystalline FeTiO_{3} synthesized at high pressure that is isostructural with acentric LiNbO_{3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below approximately 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

Composite domain walls in a multiferroic perovskite ferrite

Controlling ferromagnetism by an external electric field has been a great challenge in materials physics, for example towards the development of low-power-consumption spintronics devices. To achieve an efficient mutual control of electricity and magnetism, the use of multiferroics--materials that show both ferroelectric and ferromagnetic/antiferromagnetic order--is one of the most promising approaches. Here, we show that GdFeO(3), one of the most orthodox perovskite oxides, is not only a weak ferromagnet but also possesses a ferroelectric ground state, in which the ferroelectric polarization is generated by the striction through the exchange interaction between the Gd and Fe spins. Furthermore, in this compound, ferroelectric polarization and magnetization are successfully controlled by magnetic and electric fields, respectively. This unprecedented mutual controllability of electricity and magnetism is attributed to the unique feature of composite domain wall clamping of the respective domain walls for electric and magnetic orders. This domain wall feature generally determines the efficiency of the mutual controllability and thus could have an important role towards the application of multiferroics to practical devices.