Spin-canting and weak ferromagnetism in two novel 1D alternating chains with single cis-end-to-end azido bridges

By combining trans-4-styrylprydine （tsp） with azide system, we obtained two rare 1D cis-EE-azido-bridged compounds of [Mz（N3）4（tsp）4（H2O）2] [M = Mn （1）, Co （2）]. The magnetic study reveals that metal ions are anti-ferromagnetically coupled by cis-EE-azido-bridges and they show weak ferromagnetism below 4.0 K （1） and 4.2 K （2） due to the spin-canting caused by asymmetric magnetic interaction.

Preparation and the physical properties of antiperovskite-type compounds Cd1_xInxNNi3（n〈x〈0.2）and Cd1-yCuyNNi3（0〈y〈0.2）

Two series of Cdl-xInxNNi3 （0 〈 x 〈 0.2） and Cd1_yCuyNNi3 （0 〈 y 〈 0.2） samples were prepared from CdO, In203, CuO, and nickel powders under NH3 atmosphere at 773 K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd1-xInxNNi3 and Cd1_yCuyNNi3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9In0.1NNi3, and Cd0.9Cu0.1NNia compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd1-xInxNNi3 and Cdl-yCuyNNi3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd1-xInxNNi3 and Cd1_yCuyNNi3 samples can be well fitted to the combination of a Bloch term and a Curie-Weiss term.

Effects of Ni substitution on multiferroic properties in Bi_(5)FeTi_(3)O_(15) ceramics

The single-phase multiferroic Bi_(5)Fe_(1−x)NixTi_(3)O_(15)(BFNT-x,x=0,0.1,0.2,0.3,0.4,and 0.5)ceramics were synthesized by a sol-gel auto-combustion method,and their microstructures,ferroelectric,magnetic,and dielectric properties were investigated in detail.All samples belong to layer-perovskited Aurivillius phase containing four perovskite units sandwiched between two Bi-O layers.Ni substitution can not only improve ferroelectricity but also enhance the magnetic properties.The BFNT-0.2 sample shows the largest remnant polarization(2Pr∼11.6µC/cm^(2))and the highest remnant magnetization(2Mr∼0.244 emu/g).The enhancement of the magnetic properties may mainly originate from the spin canting of Fe/Ni-O octahedra via Dzyaloshinskii-Moriya(DM)interaction.In order to explore the influence of valance state of magnetic ions on the properties,the x-ray photoelectron spectroscopy was carried out.Furthermore,structural,ferroelectric,and magnetic transitions were also investigated.

Chiral mesostructured hematite with temperature-independent magnetism due to spin confinement

Hematite(α-Fe_(2)O_(3))is known to undergo conversion from weak ferromagnetic to antiferromagnetic as the temperature decreases below the Morin temperature(TM=250 K)due to spin moment rotation occurring during the Morin transition(MT).Herein,we endowed hematite with mesostructured chirality to maintain weak ferromagnetism without MT.Chiral mesostructured hematite(CMH)nanoparticles were prepared by a hydrothermal method with glutamic acid(Glu)as the symmetry-breaking agent.The triangular bipyramidal CMH nanoparticles were composed of helically cleaved nanoflakes with twisted crystal lattice.Field-cooled(FC)magnetization measurements showed that the magnetic moments of CMH were stabilized without MT within the temperature range of 10–300 K.Hysteresis loop measurements confirmed the weak ferromagnetism of CMH.The enhanced Dzyaloshinskii–Moriya interaction(DMI)was speculated to be responsible for the temperature-independent weak ferromagnetism,in which the spin configuration would be confined with canted antiferromagnetic coupling due to the mesostructured chirality of CMH.

Glycine-nitrate auto-combustion synthesis and magnetic properties of nanocrystalline NdAl_(x)Fe_(1-x)O_(3) perovskites

The effect of substitution of Fe^(3+) by Al^(3+) on the structure and magnetic properties of NdAl_(x)Fe_(1-x)O_(3) perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion method was studied.All samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and energy dispersive X-ray spectroscopy(EDX).The magnetic properties of the samples were investigated using a vibrating sample magnetometer(VSM).The X-ray results for all samples reveal the formation of an orthorhombic perovskite phase(space group Pbnm) with no secondary phase.The crystallite sizes of the nanoparticles are found to decrease with increasing Al content,and are in the range of 53-38 nm.SEM images show spherical nanoparticles with agglomeration.The FT-IR spectra confirm the presence of metal oxygen bonds.The M-H loop of the pristine NdFeO_(3) sample is antiferromagnetic in the a b plane with weak ferromagnetism in the c-axis.Introducing AI inclusions in the pristine polycrystal thereby creating magnetic vacancies is seen to influence the magnetic properties.The magnetic dilution results in enhanced magnetisation at low Al content;x=0.1,0.2(saturation magnetisation being 2.08 and 2.05 emu/g,respectively) compared to the pristine sample with a saturation magnetisation of 1.43 emu/g due to increased exchange interaction.Also dilution with nonmagnetic dopant induces the phase transition from weak ferromagnetic to paramagnetic depending on the impurity concentration.The coercive field for NdFeO_(3) is found to be equal to 1950 Oe and decreases with Al-substitution.These findings lay a ground work for research in tuning magnetic properties and in spintronics with potential applications in data storage,switches and electronic devices.

Ferroelectric,magnetic,and optical properties of Aurivillius compound Bi_(5)FeTi_(2.5)Co_(0.5)O_(15)

Bi_(5)FeTi_(2.5)Co_(0.5)O_(15)(BFTC)ceramics was successfully synthesized using the sol-gel method.It exhibits simultaneously visible-light response,ferroelectric and weak ferromagnetic orders at room temperature.The narrow band gap of 2.06 eV was determined via the UVevis diffuse absorption spectrum.The x-ray photoelectron spectroscopy results show that the Fe ions in the samples is 3 t and 2 t valence states while the doped Co ions is 2 t valence state.The BFTC sample undergoes a ferromagnetic-like transition at~552 K.Weak ferromagnetism is mainly due to spin-canting of Fe-based and Co-based sublattices via Dzyaloshinskii-Moriya(DM)interaction.Dielectric loss and dielectric modulus exhibit the characteristics of dielectric relaxation,which can be ascribed to oxygen/vacancy hopping.These results reveal many potentially useful physical phenomena and open a new avenue to design of novel solar-energy conversion devices and multiferroic applications.