Improved-sensitivity integral SQUID magnetometry of (Ga,Mn)N thin films in proximity to Mg-doped GaN

Gas, Katarzyna; Kunert, Gerd; Dłuźewski, P.; Jakieła, R.; Hommel, D.; Sawicki, M.

doi:10.1016/j.jallcom.2021.159119

Cited by 14 publications

(8 citation statements)

References 79 publications

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“…However, in the usual experimental conditions the investigated magnetic thin film is grown on a bulky substrate. Then, using for example, standard superconducting quantum interference device (SQUID) magnetometer, a dedicated in situ compensation of the (sapphire) substrate has to be used [23] to resolve this signal from the otherwise vastly dominating signal of the bulky substrate [24]. Detailed survey on other sources of possible artifacts during magnetic measurements were reported in Ref.…”

Section: A First Spin Orbital Reorientation Transitionmentioning

confidence: 99%

Spin orbital reorientation transitions induced by magnetic field

Sztenkiel¹

2022

Preprint

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Here we report on a new effect similar to the spin reorientation transition (SRT) that takes place at two magnetic fields of BSORT 1 and BSORT 2. The effect is observed in the magnetization curves of small Mn 3+ magnetic clusters in the wurtzite GaN (being in a paramagnetic state) calculated using crystal field model approach. The obtained results suggest that the computed magnetic anisotropy (MA) reverses its sign on increasing B across BSORT . Detailed analysis show however that MA is unchanged for high magnetic fields. We show that the observed effect arises from the interplay of the crystalline environment and the spin-orbit coupling λ ŜL , therefore we name it spin orbital reorientation transition (SORT). The value of BSORT 1 depends on the crystal field model parameters and the number of ions N in a given cluster, whereas BSORT 2 is controlled mostly by the magnitude of the spin-orbit coupling λ. The explanation of SORT is given in terms of the spin MS and orbital momentum ML contributions to the total magnetization M = MS + ML. The similar effect should also be present in other materials with not completely quenched (non zero) orbital angular momentum L, an uniaxial magnetic anisotropy and the positive value of λ.

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Section: A First Spin Orbital Reorientation Transitionmentioning

confidence: 99%

Spin orbital reorientation transitions induced by magnetic field

Sztenkiel¹

2022

Preprint

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“…The case of Al 2 O 3 substrates has been recently discussed in ref. [28], GaAs in this respect has been examined in ref. [29].…”

Section: Sample Preparationmentioning

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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“…Commercial general-purpose superconducting quantum interference devices (SQUID) have become ubiquitous experimental tools in laboratories where magnetic characterization and investigations of nanometer-scale objects is important and frequently indispensable in providing the vital insight into investigations. The range of objects include, in particular, ultrathin films [1,2], nanoparticles [3,4], and inclusions in magnetically dilute systems [5][6][7], 2D [8,9], and 1D [10,11] systems, or systems in which their surface matters [12], like topological insulators [13][14][15]. In the prevailing number of cases, the materials of interest are on a solid state substrate, which make the mounting of the sample relatively easy; a breadth of relevant experimental codes has been elaborated and methods for eliminating various pitfalls have been presented [16][17][18][19][20], which were reviewed by Pereira [21].…”

Section: Introductionmentioning

confidence: 99%

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

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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.

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Improved-sensitivity integral SQUID magnetometry of (Ga,Mn)N thin films in proximity to Mg-doped GaN

Cited by 14 publications

References 79 publications

Spin orbital reorientation transitions induced by magnetic field

Spin orbital reorientation transitions induced by magnetic field

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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