Magnetic constitution of topologically trivial thermoelectric PbTe:Cr

Gas, Katarzyna; Królicka, A.; Dybko, K.; Nowicki, P.; Khosravizadeh, Z.; Story, T.; Sawicki, M.

doi:10.1016/j.jmmm.2021.168154

Cited by 9 publications

(8 citation statements)

References 75 publications

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“…which, as an ensemble, exhibit superparamagnetic properties even at room temperature [50], yielding a convenient about 100 times stronger response at H = 10 kOe than anything else considered in this study. Actually, an adequate amount of any similar composite material can be used for this purpose.…”

Section: Absmentioning

confidence: 84%

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Pow-der Specimens Requiring the Use of Capsules

Gas

Sawicki

2021

Preprint

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Steadily growing interest in magnetic characterization of organic compounds aiming at therapeutic purposes, or of other irregular-shaped specimens calls for refinements of experimental methodology to satisfy experimental challenges. Encapsulation in capsules remains the method of choice, but its applicability in precise magnetometry is limited. This is particularly true for minute specimens in single mg range since they are outweighed by the capsules and due to large alignment errors. We present here a complete new experimental methodology which permits 30-fold in situ reduction of the signal of capsules. In practical terms it means that the standard 30 mg capsule is seen by the magnetometer as about 1 mg object, effectively opening the window for precise magnetometry of single mg specimens. The method is shown to work down to 1.8 K and in the whole range of the magnetic fields. The method is demonstrated and validated using the reciprocal space option of MPMS-SQUID magnetometers, however it can be easily incorporated in any magnetometer which can accommodate straw sample holders (i.e. the VSM-SQUID). Importantly, the improved sensitivity is accomplished relying only on the standard accessories and data reduction method provided by the SQUID manufacturer, eliminating needs for an elaborate raw data manipulations.

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Section: Absmentioning

confidence: 84%

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Pow-der Specimens Requiring the Use of Capsules

Gas

Sawicki

2021

Preprint

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“…In these regions the Mn spins stay uncoupled, so they should exert a paramagnetic (PM) response. We quantify this PM com- ponent by employing a concept developed originally for GaN:Fe composite system [49,50] and proven effective in other transition metal doped DMS systems [51].…”

Section: Resultsmentioning

confidence: 99%

Magnetic properties of wurtzite (Ga,Mn)As

Gas,

Sadowski,

Sawicki

2021

Preprint

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Here we report on detailed studies of the magnetic properties of the wurtzite (Ga,Mn)As cylindrical shells. Ga 0.94 Mn 0.06 As shells have been grown by molecular beam epitaxy at low temperature as a part of multishell cylinders overgrown on wurtzite (Ga,In)As nanowires cores, synthesized on GaAs (111)B substrates. Our studies clearly indicate the presence of a low temperature ferromagnetic coupling, which despite a reasonably high Mn contents of 6% is limited only to below 30 K. A set of dedicated measurements shows that despite a high structural quality of the material the magnetic order has a granular form, which gives rise to the dynamical slow-down characteristic to blocked superparamagnets. The lack of the long range order has been assigned to a very low hole density, caused primarily by numerous compensation donors, arsenic antisites, formed in the material due to a specific geometry of the growth of the shells on the nanowire template. The associated electrostatic disorder has formed a patchwork of spontaneously magnetized (macrospin) and nonmagnetic (paramagnetic) volumes in the material. Using high field results it has been evaluated that the total volume taken by the macrospins constitute about 2/3 of the volume of the (Ga,Mn)As whereas in the remaining 1/3 only paramagnetic Mn ions reside. By establishing the number of the uncoupled ions the two contributions were separated. The Arrott plot method applied to the superparamagnetic part yielded the first experimental assessment of the magnitude of the spin-spin coupling temperature within the macrospins in (Ga,Mn)As, T C = 28 K. In a broader view our results constitute an important contribution to the still ongoing dispute

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“…To quantify this PM component, we measure m(H) at two very low temperatures: 1.8 and 5 K, shown in Figure 15b. Clearly, the two dependencies have a Brillouinlike character at high magnetic fields, with noticeable FM-like deviations around H = 0, similar to that at 300 K. In order to accurately separate the PM signal in our turmeric sample, we invoke the fact that in most cases it is only the PM component that is responsible for changes of m(H) at low temperatures, a condition met in many magnetically composite systems in which the technique presented below worked with a very high precision [3,[48][49][50]. The diamagnetism should not depend on T, so should most of the FM contaminations, as latter are typically characterized by a very high spin coupling temperatures.…”

Section: Discussion: Validation and An Example Of The True Potentialmentioning

confidence: 99%

“…Our material of choice is a small, about 10 mg, crystallite of PbTe weakly doped with Cr. In a semiconductor matrix, chromium tends to precipitate to form ferromagnetic nanocrystals [55], which, as an ensemble, exhibit superparamagnetic properties even at room temperature [49], yielding a convenient, approximately 100 times stronger, response at H = 10 kOe than anything else considered in this study. An adequate amount of any similar composite material can be used for this purpose.…”

Section: Patentsmentioning

confidence: 94%

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Powder Specimens Requiring the Use of Capsules

Gas

Sawicki

2022

Materials

Self Cite

View full text Add to dashboard Cite

Steadily growing interest in magnetic characterization of organic compounds for therapeutic purposes or of other irregularly shaped specimens calls for refinements of experimental methodology to satisfy experimental challenges. Encapsulation in capsules remains the method of choice, but its applicability in precise magnetometry is limited. This is particularly true for minute specimens in the single milligram range as they are outweighed by the capsules and are subject to large alignment errors. We present here a completely new experimental methodology that permits 30-fold in situ reduction of the signal of capsules by substantially restoring the symmetry of the sample holder that is otherwise broken by the presence of the capsule. In practical terms it means that the standard 30 mg capsule is seen by the magnetometer as approximately a 1 mg object, effectively opening the window for precise magnetometry of single milligram specimens. The method is shown to work down to 1.8 K and in the whole range of the magnetic fields. The method is demonstrated and validated using the reciprocal space option of MPMS-SQUID magnetometers; however, it can be easily incorporated in any magnetometer that can accommodate straw sample holders (i.e., the VSM-SQUID). Importantly, the improved sensitivity is accomplished relying only on the standard accessories and data reduction method provided by the SQUID manufacturer, eliminating the need for elaborate raw data manipulations.

show abstract

Magnetic constitution of topologically trivial thermoelectric PbTe:Cr

Cited by 9 publications

References 75 publications

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Pow-der Specimens Requiring the Use of Capsules

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Pow-der Specimens Requiring the Use of Capsules

Magnetic properties of wurtzite (Ga,Mn)As

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Powder Specimens Requiring the Use of Capsules

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