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Superconductivity (SC) and ferromagnetism (FM) are normally antagonistic, and their coexistence in a single crystalline material appears to be very rare. Over a decade ago, the iron-based pnictides of doped EuFe2As2 were found to render such a coexistence, primarily because of the Fe–3d multi-orbitals which simultaneously satisfy the superconducting pairing and the ferromagnetic exchange interaction among Eu local spins. In 2016, the discovery of the iron-based superconductors AEuFe4As4 (A = Rb, Cs) provided an additional and complementary material basis for the study of the coexistence and the interplay between SC and FM. The two sibling compounds, which can be viewed as an intergrowth or a hybrid between AFe2As2 and EuFe2As2, show SC in the FeAs bilayers at T c = 35–37 K and magnetic ordering at T m ∼ 15 K in the sandwiched Eu2+-ion sheets. Below T m, the Eu2+ spins align ferromagnetically within each Eu plane, making the system as a natural atomic-thick superconductor–ferromagnet superlattice. This paper reviews the main research progress in the emerging topic during the past five years. An outlook for the future research opportunities is also presented.

It is possible to expand the applications ranges of powder material products by enhancing the performance properties of these products in addition to their manufacturability and reliability together, it’s possible by materials structures modification. In this paper, the effect of fullerene (C60) additives to iron-based powder material has been studied. All samples produced by Hot-Forging (HF) powder materials technology. Green and HF density of the obtained samples calculated by volume / weight and Archimede’s principle, respectively. The effect of technological parameters on the microstructure of carbon steels’ samples was done by an ALTAMI MET-1M metallographic microscope. Tensile test executed by using of a universal testing machine UMM –5 and the microhardness (HV10) was measured by REICHERT hardness test machine. The results showed that the HF C60 steels’ samples had higher density and strength of 0.81 and 25%, respectively, with a good plasticity in comparison with graphite steels’ samples.

The advanced persulfate oxidation technology has shown great potential in the efficient degradation of organic pollutants in water body, owing to its strong oxidation ability, easy operation and many other advantages. At present, the development of this technology focuses on the choice of activation mode of persulfate, and its essence lies in the cleavage of O-O bond in persulfate. Iron-based catalysts have been widely used in persulfate activation because of their advantages such as earth abundance, eco-friendliness and cost-effectiveness. In this paper, the methods and research progress of activating persulfate by iron-based materials (including nanometer zero-valent iron, common zero-valent iron, nanometer iron tetroxide) are reviewed. Finally, the existing problems and development direction of persulfate advanced oxidation technology in the current application are analyzed, in order to promote the development of related research work.

We report NMR experiments on heavily electron-doped Fe-based superconductor in comparison with the results on the parent Fe-based compounds. The typical parent Fe-based compound LaFe(As1-x′P x′)O exhibits the re-emergent antiferromagnetic (AFM) order at x′ ~ 0.6 (AFM2) separated from the parent AFM order at x′ =0 (AFM1). Systematic 31P-NMR study on [Sr4Sc2O6]Fe2(As1−x P x )2 (SrSc42622), which has local lattice parameters of iron-pnictogen (FePn) layer similar to the series of LaFe(As1−x′/P x′)O, also revealed that the presence of AFM1 order is universal for most of parent Fe-based compounds. In contrast, the static AFM2 order was absent in this series, however, the dynamical low-energy AFM spin fluctuations are enhanced at around x ~ 0.8, indicating that the onset of the static AFM2 is quite sensitive to the local lattice parameters of FePn layer. In order to elucidate the further universality and diversity, we have carried out 77Se-NMR measurement on Li x (NH3)yFe2−δ Se2 (Tc = 44 K) in heavily electron-doped regime. Although the spin fluctuations at low energies does not significantly develops upon cooling, the moderate spin fluctuations were extracted at high temperatures from comparison of the temperature (T) dependences of Knight shift and nuclear relaxation rate (1/T 1 T). We discuss the universality and diversity of the relationship between the Tc and the characteristics of the spin fluctuations in the Fe-based compounds from a microscopic point of the NMR measurements.

22nd Chemnitz Seminar on Materials Engineering – 22. Werkstofftechnisches Kolloquium (WTK 2021) 24th March 2021, Chemnitz, Germany 22nd Chemnitz Seminar on Materials Engineering = 22. Werkstofftechnisches Kolloquium, WTK 2021, online, 24 Mar 2021 - 24 Mar 2021; London [u.a.] : Institute of Physics, IOP conference series / Materials science and engineering 1147, 012012, 1-11 (2021). doi:10.1088/1757-899X/1147/1/012012, Published by Institute of Physics, London [u.a.]

Three iron-based powder metallurgy friction materials with different Cu content were prepared by powder metallurgy. The friction and wear properties of the materials were evaluated by the MM3000 friction and wear tester, and the effect of Cu content on the friction coefficient, wear rate and surface morphology was studied. The results show that with the increase of copper content, the matrix components are alloyed at high temperature, and the hardness and strength are significantly improved. The coefficient of dynamic friction and wear rate decreased significantly, and the coefficient of static friction and friction stability increased at high temperature. When the copper content is low, abrasive wear, spalling wear and fatigue wear are the main causes, while when the copper content is high, only slight abrasive wear occurs.

In this work, high-voltage pulsed Ar gas–liquid discharge synergizing iron-based catalyst-activated persulfate (PS) was employed to degrade methylene blue (MB) in water. The catalytic performances of two types of iron-based catalysts, namely the homogeneous catalyst Fe2+ and the heterogeneous catalyst nano-Fe3O4, were compared. Correspondingly, the plasma gas temperature and excited species were calculated and diagnosed using optical emission spectra. It was found that the introduced plasma process significantly enhanced the degradation efficiency of MB by the PS/Fe2+ and the PS/Fe3O4 systems. After 20 min of treatment, the MB degradation efficiency reaches 97.5% and 83.1% in the hybrid plasma/PS/Fe2+ and plasma/PS/Fe3O4 systems, respectively, which is 37.9% and 35.6% higher than that in the PS/Fe2+ and PS/Fe3O4 systems. The synergistic mechanism and key reactive species responsible for MB degradation in hybrid plasma/PS/Fe2+ and plasma/PS/Fe3O4 were explored using the addition of radical scavengers and control experiments under various conditions. The homogeneous catalyst Fe2+ exhibits better activation performance in PS and plasma than that of the heterogeneous catalyst nano-Fe3O4.

Iron-based nanomaterials have appeared in various cancer treatments owing to their promising functions and safety. Various sophisticated iron-based nanomaterials have been designed to exhibit great therapeutic effects through different strategies. Given the rapid progression, there is a great need to integrate the recent advances to learn about the latest innovation in this field. In this review, we classified the strategies of iron-based nanomaterials for cancer treatment into the following categories: immunotherapy, ferroptosis, magnetic hyperthermia and magneto-mechanical destruction. On the one hand, we discussed the underlining mechanism of iron-based nanomaterials in these therapies and applications; on the other hand, we analyzed the feasible combination of these applications and other therapies. Finally, the current challenges and expectation of iron-based nanomaterials in this field were highlighted.

Iron-based superconducting (IBS) racetrack coils were firstly fabricated by using 100-m 7-filamentary Ba1-xKxFe2As2 (Ba122) tapes at the Institute of High Energy Physics, Chinese Academy of Sciences (IHEP, CAS). The IBS tape was wound in parallel with stainless steel tape to withstand the high tensile hoop stress under high magnetic field. After the heat treatment, the coils were impregnated with epoxy resin. Then the IBS coils were tested in a low-temperature superconducting Common-Coil dipole magnet which provided a maximum background field of 10 T at 4.2 K. Most importantly, the best IBS racetrack coil quenched at 4.2 K and 10 T with an operating current of 65 A, which is still as high as 86.7% of critical current of the short sample at 10 T. The details of the fabrication process and performance test results were presented in this paper. The performance test demonstrated the IBS conductor is a promising candidate for the application of high field magnets especially for future high-energy accelerators.

For the iron-based powder metallurgical friction pair under high-speed braking conditions, the structural model and physical model of the friction pair were established, and the finite element software ABAQUS was used to calculate and analyze the temperature field and distribution law of the friction pair during friction braking. The results show that during friction braking, the temperature at the outer diameter of the contact surface of the friction pair is the highest, and the temperature at the inner diameter of the edge of the chip removal tank is the lowest. During braking, the temperature of friction pair increases first and then decreases with time.

In view of the iron-based powder metallurgy friction pairs under braking conditions, the temperature field and stress field of friction pairs under different rotation speeds were calculated by using the finite element software ABAQUS through building the structure and physical model of friction pairs. The temperature and stress distribution of the friction pairs under different rotation speeds were studied. The results show that in the process of friction braking, the temperature at the middle diameter of the friction contact surface is higher, and the stress at the inner diameter of the friction contact surface is the largest. With the increase of rotation speed, the distribution of temperature and stress is not changed.

The material model was established by the finite element analysis software ABAQUS. The temperature field and stress field of iron-based powder metallurgy friction pairs under the brake pressure of 0.44Mpa and 0.8MPa were calculated respectively. The variation laws of temperature and stress under two pressure conditions were compared and analyzed. The results show that with the increase of braking pressure, the stress of the friction pairs increases, but the distribution of temperature and stress fields changes little.

In the field of heterogeneous catalysis research, in situ and operando characterization techniques, i.e. characterization techniques which can be applied under realistic reaction conditions and ideally on a working catalyst, become essential in order to generate new knowledge and understanding of structure performance relationships. Only this knowledge will enable researchers to develop or rather design new catalysts for existing and novel processes without relying on an 'educated guess' approach. In combination with ever improving theoretical predictions, operando characterization techniques are expected to be the main drivers in catalyst research and associated material science in the foreseeable future. Fischer-Tropsch (FT) catalyst systems, and specifically the iron based catalysts, are highly dynamic under reaction conditions, making deductions on structure-activity relationships difficult when relying on conventional characterization techniques. In addition, various deactivation mechanisms, such as oxidation, poisoning, sintering, attrition and phase separation have been observed. As such, the FT synthesis encompasses several challenges experienced in some form or other in most catalytic applications and material science studies. The present review therefore aims to provide a comprehensive account of characterization techniques employed under (quasi) in situ and operando conditions for FT catalysts. Together with a description of the respective technique and a critical discussion of the employed reaction cell, the actual research conducted is briefly discussed. We hope that this combination will enable readers not only to get a good impression of the capabilities and limitations of the respective technique and available instrumentation but also to understand their applicability in catalysis research and maybe to be inspired to push current boundaries.

The self-healing ability of asphalt has great benefits for the service of asphalt pavement, while this ability is not significant at room temperature. This paper utilized waste steel shavings (WSS) and iron-based particles (IBP) as conductor materials, and induction heating technology to heat asphalt concretes. High temperature rutting test, low temperature cracking test and freeze-thaw splitting test were carried out to evaluate the effect of WSS and IBP on the pavement performance of asphalt concretes, and induction heating test was conducted to analyse the heating efficiency. Results shows that both WSS and IBP are beneficial to high temperature performance of asphalt concrete, but not good for low temperature performance. Besides, WSS and IBP has no significant impact on the water stability. Considering the pavement performance and induction heating efficiency, 6%-8% WSS with 2% IBP is recommended.

Non-precious metals (NPM) such as iron and nitrogen-doped carbon (Fe-N-C) have been actively studied as alternative electrocatalysts to platinum for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC). However, its low stability is associated to the structural morphology of the electrode made of Fe-N-C and its support that has restricted the mass transfer of fuel and product. In this work, it was attempted to assess the role of RGO derived from sengon wood as catalyst support to Fe-N-C catalyst, and study the effect of the Fe-N-C to RGO ratio, on the ORR activity and durability in acidic medium. This work revealed that Fe-N-C/RGO at the weight ratio of 2:0.2 demonstrated the highest onset potential of 0.91 V, with high limiting current density of 5.7 mA/cm2, owing to the uniform active site distribution on the Fe-N-C/RGO surface compared to other samples with different weight ratio. It was indicated in this work that an improve in the kinetic activity was observed with increase operating temperature from 25 to 80 °C. An electron transfer number of 3.91 indicating a complete oxygen reduction process took place on the catalyst. The durability test showed that Fe-N-C/RGO 2:0.2 retained 89 % of its current density at 0.25 V over a duration of 16000 s, higher than that of the benchmark Pt/C. These results have collectively demonstrated a high performance sustainable noble metal-free ORR catalyst for PEMFC applications with proper tailoring the mass ratio of Fe-N-C to RGO support.

Iron-based soft magnetic composites (SMCs) are promising substitutes for laminate steels in electromagnetic applications due to their excellent magnetic properties and productivity. However, the preparation process is a key factor in deciding the magnetic performance of SMCs. In this work, the Fe-based soft magnetic composites with improved soft magnetic properties were achieved by optimizing the compaction and the annealing process. Results showed that the core–shell structure of powders which would directly have an impact on the permeability and the core loss of the SMCs could be affected by the compaction and the annealing process. In addition, the magnetic properties were enhanced by tuning the microstructure. As a result, the optimal magnetic performance of the compact with high permeability and low total core loss was obtained. The real part of the permeability of the soft magnetic composites could reach a maximal value of 336.8 and a rather low core loss of 2.5 W Kg−1 (measured at 50 mT and 5 kHz). Therefore, soft magnetic composites with enhanced magnetic properties were obtained by optimizing the powder metallurgy (PM) process in this study.

Adsorption on a suitable adsorption material is the most frequently used methods in water treatment. In terms of plant operation, filtration (sorption) process represents a simple, effective and economical friendly method of heavy metals removal namely for the possibility of using a large scale of substances with a sorption ability - sorbents. Oxides, oxyhydroxides and hydroxide containing iron are among the most frequently used sorbents of the heavy metal removal. The quality of the treated water (pH, silica, phosphorus, fluorides, sulphates, total mineralization, iron and manganese, organic matter, etc.), redox conditions, the valency of metal and filtration conditions has the impacts on heavy metal removing efficiency. The objective of this work was to verify the sorption properties of granular iron-based sorption materials (CFH12, CFH18, Bayoxide E33, GEH) in removal of arsenic, antimony and nickel from drinking water. Under the given operational conditions (average concentration of arsenic in raw water 52,96 μg/L, average velocity 5.6 m/h, concentration As 10 μg/L at the outlet of media) adsorption capacity of filtration material CFH12 and Bayoxide E33 for arsenic was 1.203 mg/g and 1.463 mg/g, respectively. The limit of 10 μg/L of as was exceeded after 24048 BV and 28623 BV (Bed volume), respectively. According to the model tests (concentration of nickel in raw water of about 50 μg/L, filtration rate 5.8 m/h, concentration Ni 20 μg/L at the outlet of media, pH 7.0) the adsorption capacity of nickel for Bayoxide E33 was set to 198 μg/g, for CFH18 107.5 μg/g, GEH 97.5 μg/g and CFH12 38.1 μg/g. The limit of 20 μg/L of Ni was exceeded after 4808 BV for Bayoxide E33, 1409 BV for CFH12, 3007 BV for CFH18 and 3218 BV for GEH. For the average antimony concentration of 58.35 μg/L in raw water and filtration rate between 4.27-4.51 m/h, the limit concentration of 5 μg/l at the outlet of the sorption column was reached at the bed volume 3470 for GEH, 2225 for CFH 12 and 1274 for Bayoxide E33. The adsorption capacities were as follows: 167.8 μg/g for GEH, 105.7 μg/g for CFH12 and 90.9 μg/g for Bayoxide E33. The experiments proved that iron-based sorption materials GEH, CFH12, CFH18 and Bayoxide E33 can help reduce the concentration of heavy metals in water below the limit of the Slovak Republic Decree No. 247/2017 on Drinking Water.

Recent progress of round wires using iron-based superconductors is reviewed. Both transport and magnetic J c have been enhanced by several techniques such as purification of polycrystalline powders, high-pressure sintering (HIP), and control of drawing and sintering conditions. The present record of transport J c of round wires is realized when the wire with 122-type compounds is processed at 175 MPa with a value at 4.2 K under 100 kOe being 38 kA/cm2 using (Ba,K)Fe2As2. We also discuss HIP round wires of (Sr,K)Fe2As2 and recently fabricated CaKFe4As4. Details of the optimization of round wires to achieve large J c values are described.

In this paper, the effect of ZrO2 reinforcement and MoS2 as solid lubricant on tribological properties of iron-copper-tin composite for plain bearing application have been investigated. This paper includes two studies, one in which wt% of MoS2 is varied keeping wt% of ZrO2 constant and in another wt% of ZrO2 is varied keeping wt% of MoS2 constant to see the effect of ZrO2 as reinforcement and MoS2 as a solid lubricant for improving tribological properties of sintered Fe-Cu-Sn material. The material was prepared by sintering at temperature of 1150° C. The tribological properties of developed materials were analysed by ball on disk test.Least value of COF 0.0421 is shown by sample with 2 wt.% of MoS2 and 2 wt.% of ZrO2. Least wear rate of 0.4581x10-4 mm\Nm for sample with 2 wt.% of MoS2 and 2 wt.% ZrO2.Characterization of worn surfaces revealed abrasive and adhesive wear including third body abrasive wear, delamination and micro-ploughing in reinforced composites. The addition of MoS2 has improved tribological properties, whereas ZrO2 addition not only improved tribological properties, but also improved strength and hardnessof the composite. Maximum hardness value 208HV (701.4MPa) is shown by the composite with 2 wt.% of MoS2 and 2 wt. % of ZrO2. The findings show that the developed material could be used for antifriction andantiwear plain bearing applications.

High-performance powder metallurgy high-chromium iron-based alloy reinforced by nano-WC particles were prepared by high-energy ball milling combined with hot-press sintering. The effects of different temperatures of hot-press sintering and contents of WC reinforced phase on the friction and wear properties of the materials were studied by using the M-2000 Friction and Wear Tester under dry condition. The results show that the wear property of the material increases first, and then decreases with the growth of temperature of sintering and contents of reinforced phase. The alloy has the best wear property sintered at 1050 °C with 5wt.% WC reinforced phase. By comparing with NbC reinforced phase with similar mass fraction at 5%, finding that WC particles have more significant effect on reinforcing the wear

The finite element analysis was employed to investigate equivalent stress characteristics of iron based cladding coating and substrate, and a three-point bending simulation test was carried out. The coating was set separately on the sides of stretchand press, the distribution and change rule of equivalent stress for different coating thickness were obtained through analyzing the stress state of thecoating/substrate system and influence of coating thickness on the interfacial stress. The results show that the maximum stress of the coating/substrate system appears on the coating surface under the bending load; the thicker the coating, the higher the maximum equivalent stress of the coating/substrate system under the same press amount of the punch head.

In the previous researches, several theoretical equations were presented for calculation of buildup factor of the single layer shields. Also, the theoretical equations were offered for the two-layered shield that consist of the known materials. For other possible modes of the multi-layered shield, the buildup factor are usually calculated via experimental or simulated data. The purpose of present study is the extraction of the new theoretical equation for the gamma ray buildup factor of three-layered spherical shield made of water, concrete and iron based on the Monte Carlo calculation. To this end, the gamma ray buildup factor of the three-layered spherical shield is calculated via simulation by MCNPX computational code. Finally, the theoretical equation for gamma ray buildup factor of three-layered spherical shield vs. gamma ray buildup factors and thickness of the single-layered shields is extracted through curve fitting and regression.

We report the results of the Andreev spectroscopy of the (Co-doped Ba-122 single crystals)/metal/Pb junctions with a metal layer of Al, Pb, Ag, and Sn. We observed Andreev-like spectra for each metal layer and the junctions were identified to be (superconductor)/(normal metal) type. The spectra showed different behaviors for each metal layer. Especially in the case of Sn, the junction showed complex structure where different S/N type features were folded. We consider this behavior is due to a chemical reaction, in the interface between an iron-based superconductor and a layering metal.

The focus of this research was on gaining a fundamental understanding of the structure/property relationships that exist in an Fe-based multicomponent glass-forming alloy. While composition is one key parameter in determining the final microstructure, the specific transformation conditions (temperature and time) related to how a glass devitrifies were found to have significant effects on the development of the devitrified microstructure. Microstructural studies have revealed that recovery, relaxation, crystallization, and recrystallization phenomena are important effects which lead to large differences in the ensuing microstructure resulting in significant differences in properties such as devitrified hardness. The information gained in this study, combined with further investigations into the mechanistic processes governing these transformations, may allow for the further development of nanostructured materials with specific and targeted sets of properties.

A single band t-U-J1-J2 model is proposed as the minimum model to describe the superconductivity of the newly discovered iron-based superconductors R(O1-xFx)FeAs and RO1-xFeAs (R = La, Ce, Sm, Pr, Nd, Gd). With the mean-field approach, it is found that the pairing occurs in the d-wave channel. In the likely parameter region of the real materials, by lowering temperature, the system enters firstly the dxy superconducting phase with D4h-symmetry and then enters the time-reversal-symmetry-broken dxy + idx2-y2 superconducting phase with C4h-symmetry.

This article contains results of the study of multilayer coatings produced by laser cladding on the substrate steel 34HMA using iron based powder PR-10R6M5 as the filler material. The coatings were produced with consistent application of the tracks with fixed overlapping. The dependencies between the characteristics of tracks and the technological mode of deposition were revealed. Properties of coatings were determined for various overlapping of tracks and directions of the cladding layers.

The time-dependent Ginzburg–Landau Lawrence–Doniach model is used to investigate the superconducting fluctuation electrical conductivities. The theoretical result based on the self-consistent Gaussian approximation is used to fit the transport measurement data of iron-based superconductors F-doped LaOFeAs and BaFe2−xNixAs2. We demonstrate that LaOFeAs shows layered behavior, while BaFe2−xNixAs2 is more of a 3D feature. The conductivity in the region near Tc is well described by the theoretical formula.

We study the phase transition in Cu-substituted iron-based superconductors with a new developed real-space Green's function method. We find that Cu substitution has strong effect on the orbital-selective Mott transition introduced by the Hund's rule coupling. The redistribution of the orbital occupancy which is caused by the increase of the Hund's rule coupling, gives rise to the Mott-Hubbard metal-insulator transition in the half-filled $d_{xy}$ orbital. We also find that more and more electronic states appear inside that Mott gap of the $d_{xy}$ orbital with the increase of Cu substitution, and the in-gap states around the Fermi level are strongly localized at some specific lattice sites. Further, a distinctive phase diagram, obtained for the Cu-substituted Fe-based superconductors, displays an orbital-selective insulating phase, as a result of the cooperative effect of the Hund's rule coupling and the impurity-induced disorder., Comment: 18 pages, 8 figures

We report comprehensive angle-resolved photoemission investigations on the electronic structures and nematicity of the parent compounds of the iron-based superconductors including CeFeAsO, BaFe2As2, NaFeAs, FeSe and undoped FeSe/SrTiO3 films with 1, 2 and 20 layers. While the electronic structure near the Brillouin zone center Γ varies dramatically among different materials, the electronic structure near the Brillouin zone corners (M points), as well as their temperature dependence, are rather similar. The electronic structure near the zone corners is dominated by the electronic nematicity that gives rise to a band splitting of the dxz and dyz bands below the nematic transition temperature. A clear relation is observed between the band splitting magnitude and the onset temperature of nematicity. Our results may shed light on the origin of nematicity, its effect on the electronic structures, and its relation with superconductivity in the iron-based superconductors.

The relation between the condensation energy (CE) and T c of a phase transition reveals a fundamental nature of the transition. In view of this, the recent experimental observation of the non-BCS scaling relation of the CE vs. with about forty different samples of the Fe-based superconductors (Xing J. et al. , Phys. Rev. B , 89 (2014) 140503) was intriguing and strongly hinted at a non-BCS pairing mechanism. In this paper, we have studied the CE and T c of the multiband BCS model and found that the observed anomalous scaling relation is well reproduced by the two-band BCS model paired by a dominant repulsive interband interaction . Our result implies that this seemingly non-BCS–like scaling behavior of , on the contrary to the common expectations, is in fact a strong experimental evidence that the pairing mechanism of the Fe-based superconductors is genuinely a BCS mechanism, meaning that the Cooper pairs are formed by the itinerant carriers glued by a pairing interaction .

The character of destruction of thermal coatings during fretting has been investigated. An iron based plasma coating has been tested with oscillation amplitude from 30 to 200 microns. The tests were conducted in air. It has been determined that the main factor influencing the rate of the wear of the coating during fretting corrosion is the size of the coating area involved into the wear process. The coating exhibits high wear resistance when the amplitude of the oscillation is commensurate with the size of the sprayed particles. During destruction of the coating the leading role belongs to fatigue-oxidation processes. The wear of the coating acquires a catastrophic character when coating macro defects - pores and interlayer boundaries - are involved into the wear process.

Specific heat measurements have been successfully used to probe unconventional superconducting phases in one-band heavy-fermion and organic superconductors. We extend the method to study successive phase transitions in multi-band materials such as iron based superconductors. The signatures are multiple peaks in the specific heat, at low temperatures and high magnetic field, which can lead the experimental verification of unconventional superconducting states with non-zero total momentum., 10 pages, 2 figures