Remanence Loss Research Articles

Microstructure analysis of Ti-doped sintered Nd-Fe-B magnets

A systematic microstructure analysis has been carried out for the as-sintered and annealed Ti-doped sintered Nd-Fe-B magnets. Upon annealing, grain boundaries become more obvious and show higher Nd content and lower Fe content, leading to the improvement of coercivity. Meanwhile, the amount of Nd6Fe13Ga increases and that of Nd2Fe14B decreases, leading to a slight loss of remanence. Many rod-shaped TiB2 precipitates are found both in the as-sintered and annealed samples with most of them located at grain boundaries. There is no significant difference between the as-sintered and annealed sample in the distribution, grain shape and size of TiB2. Atomic-scale characterization of TiB2 and its neighboring area reveals the existence of an amorphous layer surrounding TiB2 with the thickness of 3.5 ± 2.5 nm. The amorphous layer is measured and analyzed to be non-ferromagnetic with obvious enrichment of Nd and Pr. Its existence is speculated to be the result of strong cohesion of Ti and B, leaving a B-poor region around TiB2 difficult to form stable crystals. The existence of TiB2 and the surrounding (Nd,Pr)-rich amorphous layer in the Ti-doped magnets is beneficial for preventing the propagation of reversed magnetic domains and improving coercivity.

Magnetic properties and Tb diffusion of sintered Nd–Fe–B magnets by suspension plasma spraying

For the first time, a TbF3 coating as a diffusion source was prepared on the surface of sintered Nd–Fe–B magnets by suspension plasma spraying. A sintered Nd–Fe–B magnet with a high coercivity and low remanence loss was obtained. The uniform and dense coating favored grain-boundary diffusion of heavy rare-earth elements, which improved the coercivity of Nd–Fe–B magnets. The effect of grain-boundary diffusion and TbF3 coating amount on the microstructure and magnetic properties of the magnet were studied. Optimal magnetic properties were obtained for a heat treatment of 900 °C for 10 h, when the TbF3 coating amount was 0.2132 mg/mm2. The coercivity reached 23.72 kOe with an increase of 60.16% compared with the original magnet, whereas the remanence did not decrease significantly. Microstructure analysis showed that a Tb-layer core–shell structure formed around the Nd2Fe14B grains after diffusion. The high magnetocrystalline anisotropy of the Tb core–shell structure formation improved the Nd–Fe–B magnet coercivity significantly. Therefore, the method of plasma spray grain-boundary diffusion is efficient and feasible.

Phase precipitation and magnetic properties of melt-spun ternary Gd2Fe14B alloy and advantages of gadolinium substitution in Y2Fe14B alloy

To take the advantage of gadolinium (Gd) in developing and manufacturing RE-permanent magnets, the magnetic properties and phase precipitation behavior of Gd2Fe14B alloys prepared by melt spinning were investigated in this work. The results show that optimally direct quenched nanocrystalline Gd2Fe14B alloy exhibits the magnetic properties with remanence Jr of 0.51 T, coercivity Hc of 187 kA/m, and maximum energy product (BH)max of 33.1 kJ/m3. It also shows excellent thermal stability with a small negative temperature coefficient of Jr (α = −0.066%/K) and a positive temperature coefficient of Hc (β = 0.171%/K). The phase precipitations of as spun Gd2Fe14B alloy during melt spinning and over-quenched amorphous Gd2Fe14B alloy during heat treatment were clarified. The magnetic properties of the crystallized alloys annealed at 800 °C are close to those of the optimized directly quenched as-spun alloys, indicating good performance stability under various processes. In addition, the role of Gd substitution in (Y1–xGdx)2Fe14B alloys was systematically studied. Gd substitution can significantly enhance the thermal stability and decrease the irreversible remanence loss of Y2Fe14B alloy. With increasing Gd content, Gd-doped Y2Fe14B alloys show continuous enhancement of Hc at elevated temperatures. The highest β value of 0.22%/K was obtained in (Y0.2Gd0.8)2Fe14B alloy at 300–400 K. Gd substitution is not only effective in improving the exchange coupling effect and corrosion resistance of Y2Fe14B alloy but also superior to Nd in terms of improving the oxidation resistance. The present work has certain instructions for designing and developing new low cost RE permanent magnets with improved thermal and environment stability.

Changes in Magnetic Properties of Magnetite Nanoparticles Upon Microbial Iron Reduction

AbstractThe magnetic signals of magnetite nanoparticles (NPs) preserved in rocks, soils, and sediments are effective index for paleoenvironmental reconstruction. It has been demonstrated that magnetite NPs can serve as a terminal electron sink for the microbial respiration (i.e., microbial iron reduction). The magnetic properties of magnetite NPs may be altered by microbial iron reduction, which is a critical but often overlooked process in paleomagnetism. In this study, three magnetite NPs with different particle sizes were reduced by a dissimilatory iron‐reducing bacterium (Shewanella oneidensis MR‐1) under a non‐growth condition mimicking that of the early Earth and modern oligotrophic environment. The changes in magnetic, chemical as well as crystallographic properties of the magnetite NPs during the microbial reduction process were examined. Our results showed that the bioreduction rate of magnetite NPs was mainly controlled by their particle size and redox state. In addition, the microbial iron reduction could affect both the crystallographic and magnetic properties of three types of magnetite NPs used herein. After bioreduction, the crystal lattice parameters and magnetic susceptibility of the magnetite NPs increased, while their remanence recording capability and coercivity decreased (i.e., “softer” magnetism). Furthermore, bioreduced magnetite NPs had a larger remanence loss near the Verwey transition region with low‐temperature magnetic analysis. These results indicate that the microbial reduction of magnetite NPs deserves attention when sedimentary magnetites are used in paleoenvironment reconstruction.

Sandwiched structure of hot-deformed Nd-Fe-B permanent magnets processed by Nd-Cu eutectic alloys diffusion

A series of sandwiched structures with different near-surface mass fractions x (x = 3 wt%, 4 wt%, 5 wt%) was employed to develop high-coercivity hot-deformed Nd-Fe-B magnets by the addition of 2 wt% Nd-Cu eutectic alloys via adjusting the middle thickness and near-surface thickness. The designed magnet with a pronounced composite structure shows a 23% increase in coercivity with a 6% loss of remanence by adjusting the sandwiched structure at 4 wt% Nd-Cu eutectic alloys in the near-surface regions. The results indicate that the near-surface Nd-Cu-rich “shell” structure can effectively suppress the magnetization reversal of overall magnets, enhancing the coercivity. With the help of loading stress, Nd-Cu liquid enriched at the near-surface regions of the sample is infiltrated into the Nd-Cu-lean middle region, resulting in a concentration gradient. Microstructure characterizations further demonstrate that the infiltrated Nd–Cu eutectic plays a critical role in inhibiting grain growth and intergranular magnetic interaction. The optimized microstructure features suppress the reversed magnetization process, which makes a positive contribution to coercivity.

Magnetic properties improvement of hot-deformed Nd–Fe–B permanent magnets by Pr–Cu eutectic pre-diffusion process

Pre-diffusion grain boundary strategy was proposed to fabricate die-upset Nd-Fe-B magnets with excellent magnetic properties. Microstructure modification of die-upset magnets played a key role in determining the magnetic properties. The effective coercivity enhancement of die-upset magnets through pre-diffusion process was enhanced from 0.076 T/wt%Pr to 0.114 T/wt%Pr with a slight remanence loss. Driven by heat, the Pr–Cu eutectic alloys were diffused into melt-spun ribbons with weakened exchange couple of matrix phase, which led to enhanced coercivity. The uniform distribution of intergranular phase was obtained in die-upset magnet with pre-diffusion process and the remanence reduction was limited with a high squareness factor. Microstructure analysis confirmed that the pre-diffusion process suppressed the longitudinal/lateral ratio of platelet-shaped grains and grain growth in die-upset process. Simultaneously, the pre-diffusion process facilitated the formation of continuous and uniform grain boundaries (GBs). The grain size was distributed over a narrow range of value with similar local critical nucleation field, which resulted in the improved squareness. The thick and continuous intergranular phase strengthened the magnetic isolation between neighboring Nd2Fe14B phases and offered more “pinning” sites for domain wall shift. The modified structure hindered the nucleation and spread of reverse domains in a low magnetic field in favor of the coercivity enhancement. The view-direct time-dependent behavior of reverse magnetic domains indicated that the coercivity mechanism for die-upset magnet was a combination of “pinning” effect and nucleation model.

Microstructure evolution of Dy69Ni31-added Nd-Fe-B sintered magnets during annealing

Intergranular adding Dy-containing powders is effective to enhance the coercivity of Nd2Fe14B-based sintered magnets with slight remanence loss due to the formation of (Nd, Dy)2Fe14B hardening shell surrounding the 2:14:1 grains. Here, the influences of post-sinter annealing (PSA) time on microstructure and coercivity of Dy69Ni31-added Nd-Fe-B magnets have been investigated. With prolonging the annealing time at 580 °C, the coercivity increases rapidly from 10.1 kOe to 16.2 kOe when the annealing time is less than 6 h and keeps nearly unchanged after longer time annealing. Longer time annealing promotes the formation of thicker Dy-enriched 2:14:1 hardening shells as well as optimized and continuous grain boundary (GB) layers, which plays positive contributions to enhance coercivity. However, the transmission electron microscope (TEM) investigations reveal that crystal structure of RE-oxides at the triple junctions changes with prolonging PSA time, transforming from double hexagonal close-packed (d-hcp) to a mixture of face-centered cubic (fcc) and ordered body-centered cubic (bcc) and to hexagonal close-packed (hcp). The latter transformation may play a negative role on coercivity enhancement, offsetting the positive contributions. These findings may provide a useful guide for engineering the microstructure of Nd-Fe-B sintered magnets.

Initial Irreversible Losses and Enhanced High‐Temperature Performance of Rare‐Earth Permanent Magnets

AbstractThere is an increasing demand for permanent magnets with high‐temperature stability. Normally, the magnets are heat treated above the operating temperature range to saturate the irreversible losses, thereby producing magnets that are stable, but with significantly degraded performance. In addition, uncertainty about the losses in differently shaped magnets causes difficulties for efficient magnetic circuit design. The variation of the initial irreversible losses with magnet shape, hysteresis loop, and operating temperature is presented here. Losses are not associated with thermal demagnetization of the whole magnet, but the damage is concentrated in an outer surface “skin” at the pole surfaces, where the demagnetizing field is nonuniform. The initial irreversible remanence loss at room temperature can be predicted as the product of the slope of the high‐temperature magnetization curvek(T) and the effective demagnetizing factor . Heat treatment with the vulnerable surfaces in contact with soft iron slabs moves the skin out of the permanent magnet and reduces the irreversible remanence loss by 30% or more, potentially improving the performance of permanent‐magnet motors, generators, bearings, and thrusters. The results deepen the understanding of the magnetism of irreversible losses and will guide the applications of permanent magnets at higher temperatures.

Coercivity improvement of hot-deformed Nd–Fe–B magnets by stress-induced Pr–Cu eutectic diffusion

Low-melting eutectic diffusion has emerged as a practical approach to enhance the coercivity of hot-deformed Nd–Fe–B magnets. Herein, we report a high-efficient stress-induced eutectic diffusion method to develop high-coercivity hot-deformed Nd–Fe–B magnets. In this method, fast Pr–Cu eutectic diffusion is accomplished with the hot-pressed and hot-deformed processes simultaneously. The coercivity of diffusion-processed magnets is substantially increased by about 33% with a slight remanence loss. The applied stress effectively controls the distribution of Pr–Cu eutectic and relieves the remanence loss. Microstructure analysis confirms that the Pr–Cu concentration gradient constructed in hot-pressed precursors effectively suppresses the near-surface grain growth during the hot-deformation process and reduces the lateral/longitudinal ratio of platelet-shaped grains. The formation of thick and continuous Pr-rich grain boundaries weakens the exchange coupling between neighboring grains, offering more “pinning” sites for domain wall displacement. Partially Pr-substitution improves the locally magnetically “hardening” of 2:14:1 main phases. The optimized structural and magnetic characterizations hinder the nucleation and propagation of reversed magnetic domains at low magnetic fields, which is beneficial to coercivity enhancement. These findings clarify the characteristics of the stress-induced diffusion method and give a new insight into the structural modulation for Nd–Fe–B materials.

Graphene Nanoplatelets as Novel Additive to Enhance Coercivity of Hot‐Deformed Magnets by Tuning Microstructures

AbstractIn this work an effective approach of tuning the microstructures and enhancing the coercivity of hot‐deformed Nd‐Fe‐B magnets without obvious remanence loss by adding graphene nanoplatelets (GNPs) is proposed. Based on the microstructure characterization, the adjacent Nd2Fe14B grains on the interfaces are in polygonal shape with the small grain size less than 100 nm, and the GNPs are mainly around the interfaces of the melt‐spun ribbons. Due to the outstanding mechanical, electrical, and thermal properties, the GNPs can act as the steric hindrance additives and thermal conducting medium, which is helpful to restrain the growth of Nd2Fe14B grains effectively and decrease or even eliminate the coarse grains region. As a result, the coercivity of hot‐deformed Nd‐Fe‐B magnets is enhanced remarkably with their refined microstructure; the coercivity is substantially improved by 33.2% from 785 to 1046 kA m−1 with the GNPs additive amount from 0 to 0.2 wt%, while the remanence loss is also as low as 1.56% from 1.28 to 1.26 T. This work reported here suggests that the GNPs have great potentials in fabricating materials with controlled grain growth properties.

Characterization of the magnetic properties of NdFeB thick films exposed to elevated temperatures

Hard magnetic films used in magnetic micro-systems may be exposed to elevated temperatures during film and system fabrication and also during use of the micro-system. In this work, we studied the influence of temperature on the magnetic properties of 10 μm thick out-of-plane textured NdFeB films fabricated by high rate triode sputtering. Out-of-plane hysteresis loops were measured in the range 300K – 650K to establish the temperature dependence of coercivity, magnetization at 7 T and remanent magnetization. Thermal demagnetization was measured and magnetization losses were recorded from 350K in films heated under zero or low (-0.1 T) external field and from 325 K for films heated under an external field of -0.5 T. The effect of thermal cycling under zero field on the remanent magnetization was also studied and it was found that cycling between room temperature and 323 K did not lead to any significant loss in remanence at room temperature, while a 4% drop is recorded when the sample is cycled between RT and 343K. Measurement of hysteresis loops at room temperature following exposure to elevated temperatures reveals that while remanent magnetisation is practically recovered in all cases, irreversible losses in coercivity occur (6.7 % following heating to 650K, and 1.3 % following heating to 343K). The relevance of these results is discussed in terms of system fabrication and use.

On the role of magnetising frequency and magnetic field intensity on hysteresis loop characteristics

The goal of present research work is to study the variation in the shape of hysteresis loop owing to change in the analysis parameter i.e., magnetising frequency and applied magnetic field strength upon pack carburised low carbon steel samples. Pack carburised heat treatment performed at three different temperatures to induce varying hardness into steel samples. Hysteresis loop characteristics such as coercivity, permeability, power loss and remanence were measured in a wide range of magnetising frequency and magnetic field intensity. Coercivity is observed to increase with increase in magnetising frequency and applied field strength. In low-frequency range ( 1 Hz) results into increase in remanence and power loss. However, with an increase in magnetic field strength both remanence and power loss were found to increase.

Low-temperature magnetic properties of monoclinic pyrrhotite with particular relevance to the Besnus transition

Monoclinic pyrrhotite (Fe7S8) owes its ferrimagnetism to an ordered array of Fe vacancies. Its magnetic properties change markedly around 30 K, in what is known as the Besnus transition. Plausible explanations for the Besnus transition are either due to changes in crystalline anisotropy from a transformation in crystal symmetry or from the establishment of a two-phase system with magnetic interaction between the two phases. To help resolve this discrepancy, we measured hysteresis loops every 5° and backfield curves every 10° in the basal plane of an oriented single crystal of monoclinic pyrrhotite at 300 K and every 2 K from 50 K through the Besnus transition until 20 K. Between 50 and 30 K, hysteresis loops possess double inflections between crystallographic a-axes and only a single inflection parallel to the a-axes. Magnetization energy calculations and relative differences of the loops show a sixfold symmetry in this temperature range. We propose that the inflections stem from magnetic axis switching, which is both field and temperature dependent, in a manner somewhat analogous to an isotropic point where magnetocrystalline constants change their sign. The Besnus transition is best characterized by changes in magnetic remanence and coercivity over a 6° temperature span (28–34 K) with a maximum rate of change at 30 K. A surprising yet puzzling finding is that the coercivity ratio becomes less than unity below the transition when fourfold symmetry arises. Because the changes in magnetic parameters are linked to the crystal structure, we conclude the Besnus transition owes its origin to a distortion of the crystallographic axes below 30 K rather than an apparition of a two-phase system. An isothermal magnetization of natural pyrrhotite cycled from room temperature to successively lower temperatures through the Besnus transition decreases 2–4 times less than equivalent grain sizes of magnetite, with less than a 10 per cent loss in remanence between 300 and 150 K in pseudo-single-domain (PSD) pyrrhotite. As PSD monoclinic pyrrhotite carries the magnetic remanence in some meteorites, it is likely that low-temperature cycling in space then warming to ambient conditions at the Earth's surface will have only a minor influence on palaeointensity values derived from those meteorites.

Substitution of Nd with other rare earth elements in melt spun Nd2Fe14B magnets

This is a contemporary study of rapidly quenched Nd1.6X0.4Fe14B magnetic materials (where X= Nd, Y, Ce, La, Pr, Gd and Ho). A 20% substitution of the Nd component from Nd2Fe14B can bring about some commercial advantage. However, there will be some compromise to the magnetic performance. Light rare earth elements are definitely more abundant (Y, Ce, La) than the heavier rare earth elements, but when they are included in RE2Fe14B magnets they tend to lower magnetic performance and thermal stability. Substituting heavy rare earth elements (Gd, Ho) for Nd in Nd2Fe14B improves the thermal stability of magnets but causes a loss in magnet remanence.

Coercivity enhancement of Nd–Fe–B sintered magnets with intergranular adding (Pr, Dy, Cu)−Hx powders

Forming Nd2Fe14B/(Nd, Dy)2Fe14B core–shell structure by intergranular adding Dy-containing sources into Nd–Fe–B sintered magnets is effective to improve coercivity and to minimize remanence loss simultaneously. However, the excessive Dy located in the intergranular regions has nearly no hard magnetic contribution, causing its low utilization efficiency. In this work, diluted Dy powders (Pr37Dy30Cu33)–Hx were prepared and incorporated into Nd–Fe–B sintered magnets via a dual-alloy approach. The coercivity increases rapidly from 15.0 to 18.2kOe by 21.3% with 2.0wt% (Pr, Dy, Cu)–Hx addition (the equivalent Dy is only 0.32at%). The deduced coercivity incremental ratio is 10.0kOe per unit Dy at%. Dehydrogenation reaction of (Pr, Dy, Cu)–Hx occurs during sintering, which favors Dy diffusion towards the 2:14:1 phase grains as well as smoothing the grain boundaries (GBs). The enhanced local anisotropic field and the well decoupled 2:14:1 phase grains contribute to such rapid coercivity enhancement. This work suggests that adding diluted Dy hydrides is promising for fabricating high coercivity Nd–Fe–B sintered magnets with less heavy rare-earth consumption.

Coercivity enhancements of Nd–Fe–B sintered magnets by diffusing DyHx along different axes

Diffusing heavy rare earth elements along the grain boundaries (GBs) for Nd2Fe14B-type sintered magnets serves as an effective method to enhance coercivity and to minimize remanence loss simultaneously. Considering the texture anisotropy of Nd-rich GB phases, the coercivity incremental difference by diffusing DyHx fine powders along or perpendicular to the <0 0 1 > easy axis (c-axis) has been investigated. The coercivity increases more rapidly to 20.61 kOe (5.76 kOe higher than that of the as-sintered state) when diffusing along the c-axis than that diffusing perpendicular to c-axis (18.85 kOe, 4.00 kOe higher than the as-sintered state). Microstructural investigation reveals that Dy diffuses more easily towards the magnet inner part when treating along the c-axis than that for the perpendicular case due to the anisotropic distribution of the Nd-rich phase. This is verified by a higher Dy content at equivalent diffusing depth and a much deeper final diffusion distance. The local Dy-containing fractions with a stronger anisotropy field are richer for the magnet treated along the c-axis, leading to the much rapider coercivity enhancement. This work reveals that diffusion heavy rare earth along the c-axis is more effective to enhance coercivity for aligned Nd–Fe–B sintered magnets.

Effects of Dy71.5Fe28.5 intergranular addition on the microstructure and the corrosion resistance of Nd–Fe–B sintered magnets

To satisfy high-temperature applications, heavy rare-earth (RE) Dy is commonly introduced into the Nd–Fe–B sintered magnets to improve the coercivity. In addition to forming (Nd, Dy)2Fe14B, Dy also exists in the intergranular RE-rich phase. Hence, understanding the effect of Dy on the electrochemical characteristics of the RE-rich phase and corrosion resistance of the magnet is of importance. In this work, eutectic alloy Dy71.5Fe28.5 powders were added into the (Pr0.2Nd0.8)12.3FebalB6.1 magnet through binary-alloy approach to investigate the corrosion resistance of the magnet in electrochemical and hot/humid environments. The results demonstrate that Dy is enriched in the intergranular phase, improving its electrode potential and stability due to the higher electrode potential of Dy than Nd or Pr. As a consequence, the electrode potential difference between the 2:14:1 phase and the RE-rich phase is reduced, improving the corrosion resistance. Furthermore, formation of (Pr, Nd, Dy)2Fe14B shell with stronger local anisotropy surrounding the 2:14:1 phase grains improves the coercivity with a slight remanence loss. Therefore, intergranular adding Dy–Fe alloy powders can obtain both high magnetic properties and good corrosion resistance simultaneously.

High-coercivity hot-deformed Nd–Fe–B permanent magnets processed by Nd–Cu eutectic diffusion under expansion constraint

The application of expansion constraint during the grain-boundary diffusion process using Nd70Cu30 eutectic alloy minimizes the remanence loss for the coercivity enhancement by optimizing the volume fraction of the Nd(Cu)-rich non-ferromagnetic intergranular layer. The diffusion-processed sample exhibits μ0Hc ∼ 2 T, μ0Mr = 1.36 T and (BH)max = 358 kJ m−3 at room temperature. Because of the low-temperature coefficient of coercivity, the magnet showed (BH)max ∼ 191 kJ m−3 at 200 °C, which is superior to that of Dy-containing high-coercivity sintered magnets.

A strong angular dependence of magnetic properties of magnetosome chains: Implications for rock magnetism and paleomagnetism

Single‐domain magnetite particles produced by magnetotactic bacteria (magnetosomes) and aligned in chains are of great interest in the biosciences and geosciences. Here, we investigated angular variation of magnetic properties of aligned Magnetospirillum magneticum AMB‐1 cells, each of which contains one single fragmental chain of magnetosomes. With measurements at increasing angles from the chain direction, we observed that (i) the hysteresis loop gradually changes from nearly rectangular to a ramp‐like shape (e.g., Bc and remanence decrease), (ii) the acquisition and demagnetization curves of IRM shift toward higher fields (e.g., Bcr increases), and (iii) the FORC diagram shifts toward higher coercivity fields (e.g., Bc,FORC increases). For low‐temperature results, compared to unoriented samples, the samples containing aligned chains have a much lower remanence loss of field‐cooled (δFC) and zero‐field‐cooled (δZFC) remanence upon warming through the Verwey transition, higher δ‐ratio (δ = δFC/δZFC) for the measurement parallel to the chain direction, and lower δ‐ratio, larger δFC and δZFC values for the perpendicular measurement. Micromagnetic simulations confirm the experimental observations and reveal that the magnetization reversal of magnetosome chain appears to be noncoherent at low angles and coherent at high angles. The simulations also demonstrate that the angular dependence of magnetic properties is related to the dispersion degree of individual chains, indicating that effects of anisotropy need to be accounted for when using rock magnetism to identify magnetosomes or magnetofossils once they have been preserved in aligned chains. Additionally, this study experimentally demonstrates an empirical correspondence of the parameter Bc,FORC to Bcr rather than Bc, at least for magnetite chains with strong shape anisotropy. This suggests FORC analysis is a good discriminant of magnetofossils in sediments and rocks.

Synthesis, magnetic and dielectric properties of Er–Ni doped Sr-hexaferrite nanomaterials for applications in High density recording media and microwave devices

A sol–gel combustion method has been successfully employed for the synthesis of Sr-hexaferrite nanomaterials doped with Er3+ and Ni2+ at strontium and iron sites, respectively. The X-ray diffraction analysis confirmed the single magnetoplumbite phase and the crystallite size was found to be in the range of 14–16nm, suitable for obtaining signal-to-noise ratio in the high density recording media. The magnetic properties such as saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) were calculated from hysteresis loops. Ms, Mr and Hc are observed to increase with the Er–Ni content. The dielectric constant (ε´) and dielectric loss (tanδ) is found to decrease with the increase in frequency and is explained on the basis of Maxwell–Wagner and Koops theory. The decrease in dielectric constant and dielectric loss but increase in saturation magnetization and remanence with Er–Ni content suggests that the materials are suitable for applications in microwave devices and high density recording media .