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Transport and loss of beam injected energetic particles (EPs) due to three-dimensional perturbations, associated with the external kink (XK) instability and fishbone-like mode (FLM), are numerically investigated utilizing the guiding center following code ORBIT for static toroidal plasmas in HL-2A. The perturbation structure for the XK is computed by the MARS-F code and then mapped to the Boozer coordinates as defined in ORBIT. The simulation shows that the EP profile experiences a significant change in the middle of the plasma column, when the XK-induced radial magnetic field perturbation amplitude, normalized by the equilibrium field, exceeds a threshold value of about 10 − 2 . The EP transport is found to be dominated by a diffusion process instead of convection. Furthermore, by scanning the perturbation frequency as a free parameter while maintaining the XK mode structure (thus mimicking the FLM as observed in DIII-D and JT-60U tokamaks), redistribution and loss of EPs are found to be substantially enhanced due to strong resonances between the FLM and EPs, when the mode frequency exceeds a threshold value of ∼2 kHz for the case considered. For either XK or FLM, the response of passing EPs to the perturbation is dominant due to the assumed tangential neutral beam injection. Most lost EPs due to these instabilities are initially passing particles but are eventually lost through trapped orbits. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel tensile tests with applied external magnetic field were performed. • The magnetic field has minimum effect on the tensile properties of Eurofer-97. • No change in the fracture surface is observed. • The importance of performing creep tests with magnetic fields is discussed. Abstract Eurofer-97 is the main structural material targeted for the EU DEMO fusion tokamak and will be exposed to magnetic fields up to ˜10 T during operation. It is therefore necessary to understand the effect of magnetic fields on the mechanical properties of the Eurofer-97. We perform 30 uniaxial tensile tests with and without a transverse 1.5 T magnetic field at room temperature. Statistical results reveal that the magnetic field increases the value of proportionality limit by ˜2.6% (from 514 ± 4.5 MPa to 528 ± 10 MPa), but has minimum (<1%) effect on the ultimate tensile strength and elongation of this Eurofer-97. No clear change in the fracture surface is observed. [ABSTRACT FROM AUTHOR]

The Al3+ doping effects on the ferromagnetic metallic state of La 0.55 Ca 0.45 MnO 3 have been studied by preparing the La 0.55 Ca 0.45 Mn 1- x Al x O 3- δ (x = 0, 0.05, 0.1, 0.15) ceramics. Various measurements such as ac susceptibility, relaxation, magnetization and resistivity were performed to study the magnetic and magnetotransport properties. The magnetic disorder produced by the Al3+ dopants and the oxygen vacancies suppress the long range ferromagnetic ordering and induce a short range charge ordered antiferromagnetic clusters, leading to a phase separated behavior in the Al3+-doped samples. A Griffith-like behavior is observed due to the occurrence of short range ferromagnetic clusters in the paramagnetic phase. The 15% Al3+ doping sample exhibits a spin-glass state. The 10% Al3+ doping system is blocked in a metastable state upon cooling at zero field, and a sharp metamagnetic transition is induced by applying a high magnetic field, in which the antiferromagnetic phase is transformed into ferromagnetic phase and the ferromagnetic clusters grow in size. The ferromagnetic domains grows rapidly when applying a high magnetic field. Once the conducting ferromagnetic domains are interconnected throughout the sample, a percolative insulating-to-metallic state transition would occur, accompanied by a sharp drop in resistivity. • Al3+ doping induces charge ordered AFM clusters in La 0.55 Ca 0.45 Mn 1- x Al x O 3- δ. • The magnetic disorder caused by Al3+ doping suppresses the long rang FM ordering. • The AFM clusters transform into FM phase via field driven metamagnetic transition. • Percolative insulator-metallic transition occurs when applying a magnetic field up to H C. [ABSTRACT FROM AUTHOR]

Magnetization relaxation, ac susceptibility, dc magnetization and magnetoelectrical transport measurements have been carried out on Al3+-doped manganites La 0.5 Ca 0.5 Mn 1- x Al x O 3- δ (x = 0.05, 0.07, 0.09, 0.10, 0.15). Experimental results suggest that nonmagnetic Al3+ substituting Mn suppresses the ferromagnetic phase and induces a charge ordered antiferromagnetic phase. The coexistence and competition of these two kinds of interactions result in a spin-glass like state in x = 0.1 and 0.15 system. Obvious hysteresis was observed in both magnetization and resistivity versus temperature and magnetic field curves, suggesting an inhomogeneous metastable phase transition. Upon applying a magnetic field of H C A-F, the Al3+-doped samples undergo an irreversible metamagnetic transition from the charge ordering antiferromagnetic insulating to ferromagnetic metallic phase in the low temperature region. Phase diagram in the H C - T plane has been determined according to the magnetization and magnetoelectric transport measurements. The magnetic disorders and antiferromagnetic matrix produced by Al3+ dopants and spontaneous oxygen vacancies play an important role in the pinning of the FM phase. [ABSTRACT FROM AUTHOR]

Abstact: Magnetic properties of Mn-doped ZnO (Zn0.98Mn0.02O) bulk materials prepared by the solid state reaction method were investigated by measuring magnetization as functions of temperature and magnetic field. The results indicate that the samples sintered in Ar gas show ferromagnetic behavior at room temperatures, but it disappears in samples sintered in air. Even for ferromagnetic samples, the obtained saturation value of magnetization is much smaller than theoretical value, suggesting the possibility of that there was a strong anti-ferromagnetic exchange coupling in this kind of compounds. [Copyright &y& Elsevier]

We show that the replacement of Mn with Al strongly affects the magnetization and electrical transport behaviors in La 0.5 Ca 0.5 Mn 1- x Al x O 3- δ (x = 0, 0.05, 0.07 and 0.09). Nonmagnetic Al3+ ions substitution at Mn sites dilutes Mn3+-O2--Mn4+ network, thus suppresses the ferromagnetic metallic state in La 0.5 Ca 0.5 MnO 3- δ and causes a phase separation phenomenon, in which ferromagnetic phase coexists with antiferromagnetic charge ordered phase at low temperatures. With applying sufficiently high magnetic field, step-like metamagnetic transitions were observed in x = 0.05–0.09 systems below helium temperature, in which the antiferromagnetic charge ordered phase collapsed into ferromagnetic phase. Corresponding to the sharp step-like metamagnetic transitions, the resistivity decreases dramatically with increasing magnetic field, exhibiting a percolative insulator-metal transition. The variation of temperature and magnetic field changes the relative fractions of ferromagnetic and charge ordering phases, and percolative insulator-metal transition occurs due to the development of percolation paths between the growing FM domains. [ABSTRACT FROM AUTHOR]

Abstract We investigate the electrical and magnetic properties of the Bi 2 Fe 4- x Ga x O 9 (0 ≤ x ≤ 1.6) polycrystalline samples synthesized via solid-state reaction technique. Magnetic susceptibility measurements reveal that lightly doped samples (x < 0.8) undergo successive transitions, from high-temperature paramagnetic to antiferromagnetic phase followed by a low-temperature spin-glass state while the samples with heavy doping (x > 0.8) demonstrate paramagnetic to spin-glass (SG) transition. The variation of irreversible temperature obtained from zero field cooling (ZFC) and field cooling (FC) susceptibilities versus measured magnetic field and low-temperature magnetic hysteresis (M-H) loops support the existence of spin-glass phase. The dielectric constant (Ɛ r) of Bi 2 Fe 4-x Ga x O 9 with Ga-dilution reveals a weak-temperature sensitivity in high-temperature range (300 K ≤ T ≤ 550 K), which is advantageous for high temperature capacitor applications and electronic devices. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties of 1.5at% Fe-doped NiO bulk samples were investigated. The samples were prepared by sintering the corresponding precursor in air at temperatures between 400 and 800°C for 6h. The synthesis was by a chemical co-precipitation and post-thermal decomposition method. In order to allow a comparison, a NiO/0.76at% NiFe2O4 mixture was also prepared. The X-ray diffraction pattern shows that the samples that were sintered at 400 and 600°C remain single phase. As the sintering temperature increased to 800°C, however, the sample becomes a mixture of NiO and NiFe2O4 ferrite phases. The samples were investigated by measuring their magnetization as a function of magnetic field. The samples sintered between 400 and 800°C and the one mixed directly with NiFe2O4 nanoparticles show a coercivity value of H c≈200, 325, 350 and 110Oe, respectively. The magnetic properties of the samples depend strongly on the sintering temperature. Simultaneously, the field-cooling hysteresis loop shift also observed after cooling the sample sintered at 600°C to low temperature suggests the possibility of the existence of a ferromagnetic/antiferromagnetic exchange coupling. [Copyright &y& Elsevier]

Abstract: We report on a heterogeneous precipitation method to modify the surfaces of La0.67Ca0.33MnO3 (LCMO) grains with CuO. It is shown that such a modification causes transport and magnetoresistance (MR) properties of the composites largely different from that observed in pure LCMO granular system. Especially, a significant enhancement in MR is observed near the insulator–metal transition temperature (T IM). The maximum MR reaches as high as ∼88 and ∼90% at a low magnetic field of 0.3T for the modified samples of LCMO/xCuO with x =4 and 15mol%, respectively. Compared to pure LCMO, the CuO-modified samples have a substantial decrease in resistivity (ρ) at the temperature regions apart T IM. Furthermore, for the x =4% sample, a considerable thermal hysteresis is observed at the same temperature region where abnormal MR effect appears. On the basis of magnetization measurement and structural analysis, a possible interpretation for the experimental observations is presented. [Copyright &y& Elsevier]

Abstract: The composites with the nominal composition of (1− x)La2/3Ca1/3MnO3 (LCMO)/xSb2O5 were fabricated, and their electrical transport and magnetoresistance (MR) behavior were investigated. Experimental results show that the metal–insulator transition temperature (T MI) and resitivity (ρ) of the composites are largely dependent on Sb2O5 addition level x. T MI shifts downwards and ρ increases with the increase of x at the range of x ≤3%, but T MI shifts upwards and ρ decreases with further increasing of x ≥3%. The high temperature (T > T MI) semi-conducting part of the ρ data follow a small polaron hopping (SPH) conduction mechanism, and the metallic behavior of the samples (T < T MI) fits the model in terms of electron–magnon scattering of the carriers. Furthermore, the MR effect can be largely enhanced over a wide temperature range in the composites compared with pure LCMO. At 3T field, the MR rises from a base value ∼46%, for pure LCMO, to a maximum value of ∼86.7% for the case of x =3%. It is argued that the enhancement of MR effect is attributed to the enhanced spin-polarized tunneling, which is manipulated by magnetic disorder especially at LCMO grain boundaries caused by Sb2O5 addition. [Copyright &y& Elsevier]

Abstract: At zero magnetic field, a series of five phase transitions occur in . The Néel temperature, , is followed by four additional phase changes at , , , and . The different phases are distinguished by the commensurability of the b-component of its spin density wave vector. We investigate the stability of these various phases under magnetic fields through dielectric constant and magnetic susceptibility anomalies. The field-temperature phase diagram of is completely resolved. The complexity of the phase diagram results from the competition of different magnetic states with almost equal ground state energies due to competing exchange interactions and frustration. [Copyright &y& Elsevier]

• The charge ordering (CO) phase in Nd 0.6- x Bi x Ca 0.4 MnO 3 is enhanced with Bi3+ doping. • The enhancement of CO phase is explained by the s-p hybridization model. • Pulsed high magnetic fields up to 50 T were used to study the CO phase melting. • H C - T phase diagrams of Nd 0.6- x Bi x Ca 0.4 MnO 3 (0 ≤ x ≤ 0.4) were obtained. We report the doping effects and pulsed high magnetic field-induced charge ordering to ferromagnetic phase transitions in manganites Nd 0.6- x Bi x Ca 0.4 MnO 3 (0 ≤ x ≤ 0.4). The experimental results reveal that the charge ordering is significantly enhanced upon Bi3+ doping, and the charge ordering temperature increases with increasing Bi3+ content. With applying pulsed high magnetic field, the charge ordering phase collapses into ferromagnetic phase through a metamagnetic transition. The phase diagram of Nd 0.6- x Bi x Ca 0.4 MnO 3 has been determined by the high magnetic field studies, in which the charge ordering and ferromagnetic phase boundary is clearly figured out. The critical fields for melting the charge ordering phase of Nd 0.6- x Bi x Ca 0.4 MnO 3 increase significantly with increasing Bi3+ content, which is revealed to reach up to 33.5 T for the sample with x = 0.3. Based on the hybridization between Bi-6s orbitals and O-2p orbitals, we assume that the 6s2 lone-pair character of Bi3+ plays a crucial role in favoring the charge ordering in Nd 0.6- x Bi x Ca 0.4 MnO 3 (0 ≤ x ≤ 0.4). [ABSTRACT FROM AUTHOR]