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Register a new userOn the magnetism of the C14 Nb0.975Fe2.025 Laves phase compound: Determination of the H-T phase diagram
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A C14 Nb0.975Fe2.025 Laves phase compound was investigated aimed at determining the H-T magnetic phase diagram. Magnetization, M, and AC magnetic susceptibility measurements were performed. Concerning the former field-cooled and zero-field-cooled M-curves were recorded in the temperature range of 2-200K and in applied magnetic field, H, up to 1000 Oe, isothermal M(H) curves at 2 K, 5 K, 50 K, 80 K and 110 K as well as hysteresis loops at several temperatures over the field range of -10 to +10kOe. Regarding the AC susceptibility, both real and imaginary components were registered as a function of increasing temperature in the interval of 2 K - 150 K at the frequencies of the oscillating field, f, from 3 Hz up to 999 Hz. An influence of the external DC magnetic field, H, on the temperature dependence of the AC susceptibility was investigated, too. The measurements clearly demonstrated that the magnetism of the studied sample is weak, itinerant and has a reentrant character. Based on the obtained results a magnetic phase diagram has been constructed in the H-T coordinates.
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C14 Nb(Fe89.4Al10.6)2 Laves phase intermetallic compound was investigated by DC magnetization (M) measurements performed in the temperature (T) interval of 20 to 175 K,under an applied magnetic field (H) ranging between 50 and 1250 Oe. Magnetization curves were recorded in the field-cooled (FC) and in the zero-field-cooled (ZFC) modes. They clearly showed an irreversible character that vanished at H=1250 Oe. Both magnetization curves exhibited well-defined peaks around T_N =72.3 K whose positions were H-independent, so they were identified as the compounds Neel temperature. The existence of irreversibility which decreases with H testify to a re-entrant character of magnetism in the studied compound. An increase of both MFC and MZFC observed below TN likely indicates a mixed i.e. ferromagnetic and antiferromagnetic ground magnetic state of the studied system.
In-field DC and AC magnetization measurements were carried out on a sigma-phase Fe55Re45 intermetallic compound aimed at determination of the magnetic phase diagram in the H-T plane. Field cooled, M_FC, and zero-field cooled, M_ZFC, DC magnetization curves were measured in the magnetic field, H, up to 1200 Oe. AC magnetic susceptibility measurements were carried out at a constant frequency of 1465 Hz under DC fields up to H=500 Oe. The obtained results provide evidences for re-entrant magnetism in the investigated sample. The magnetic phase diagrams in the H-T plane have been outlined based on characteristic temperatures determined from the DC and AC measurements. The phase diagrams are similar yet not identical. The main difference is that in the DC diagram constructed there are two cross-over transitions within the strong-irreversibility spin-glass state, whereas in the AC susceptibility based diagram only one transition is observed. The border lines (irreversibility, cross-over) can be described in terms of the power laws.
Magnetization measurements were carried out in the in field-cooled (FC) and in zero-field-cooled (ZFC) conditions versus temperature, T, and external magnetic field, H, on a sigma-phase Fe47Mo53 compound. Analysis of the measured M_FC and M_ZFC curves yielded values of characteristic temperatures: magnetic ordering (Curie) temperature, T_C, irreversibility temperature, T_ir, temperature of the maximum in M_ZFC, T_m, identified as the N.eel (T_N) temperature, and cross-over temperature, T_co. Based on these temperatures a magnetic phase diagram in the H-T plane was outlined. The field dependences of the characteristic temperatures viz. of the irreversibility and of the cross-over temperatures were described in terms of a power law with the exponent 0.5(1). In the whole range of H i.e. up to 800 Oe, except the one H>50 Oe, a rare double re-entrant transition viz. PM-FM-AF-SG takes place. For small fields i.e. H<50 Oe a single re-entrant transition viz. PM-FM-SG is revealed.
The quasi-one-dimensional antiferromagnetic Ising-like compound BaCo2V2O8 has been shown to be describable by the Tomonaga-Luttinger liquid theory in its gapless phase induced by a magnetic field applied along the Ising axis. Above 3.9 T, this leads to an exotic field-induced low-temperature magnetic order, made of a longitudinal incommensurate spin-density wave, stabilized by weak interchain interactions. By single-crystal neutron diffraction we explore the destabilization of this phase at a higher magnetic field. We evidence a transition at around 8.5 T towards a more conventional magnetic structure with antiferromagnetic components in the plane perpendicular to the magnetic field. The phase diagram boundaries and the nature of this second field-induced phase are discussed with respect to previous results obtained by means of nuclear magnetic resonance and electron spin resonance, and in the framework of the simple model based on the Tomonaga-Luttinger liquid theory, which obviously has to be refined in this complex system.
We present magnetization measurements on Sr4Ru3O10 as a function of temperature and magnetic field applied perpendicular to the magnetic easy $c$-axis inside the ferromagnetic phase. Peculiar metamagnetism evolves in Sr4Ru3O10 below the ferromagnetic transition $T_{C}$ as a double step in the magnetization at two critical fields $H_{c1}$ and $H_{c2}$. We map the $H-T$ phase diagram with special focus on the temperature range 50,K $le T le T_{C}$. We find that the critical field $H_{c1}(T)$ connects the field and temperature axes of the phase diagram, whereas the $H_{c2}$ boundary starts at 2.8,T for the lowest temperatures and ends in a critical endpoint at (1,T; 80,K). We conclude from the temperature dependence of the ratio $frac{Hc1}{Hc2}(T)$ that the double metamagnetic transition is an intrinisc effect of the material and it is not caused by sample stacking faults such as twinning or partial in-plane rotation between layers.
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